Gas separation membrane module and method for gas separation

ABSTRACT

A process for producing nitrogen-rich air by feeding high temperature air at 150° C. or more to an air separation membrane module is described. After being placed at 175° C. for two hours, the air separation module exhibits a shape-retention ratio of 95% or more in one embodiment. The nitrogen-rich air can be fed to a fuel tank for an aircraft, for example.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 14/494,747, filed Sep. 24, 2014, which is a continuation of U.S.application Ser. No. 13/288,095, filed Nov. 3, 2011, which claims thebenefit of Japanese Patent Application Nos. 2010-247779, filed Nov. 4,2010; 2010-247931, filed Nov. 4, 2010; 2010-274619, filed Dec. 9, 2010,2011-122285, filed May 31, 2011; 2011-207538, filed Sep. 22, 2011;2011-207647, filed Sep. 22, 2011; 2011-227101, filed Oct. 14, 2011; and2011-239388, filed Oct. 31, 2011.

TECHNICAL FIELD

The present invention relates to a gas separation membrane module and agas separation method for separating gases using a number of hollowfiber membranes with selective permeability.

BACKGROUND ART

A separation membrane module using a separation membrane with selectivepermeability for gas separation (for example, separation of oxygen,nitrogen, hydrogen, water vapor, carbon dioxide, organic vapor or thelike) can be of plate and frame type, of tubular type, of hollow fibertype or the like. Among these, a hollow-fiber type gas separationmembrane module is industrially excellent because it is not onlyadvantageous in its largest membrane area per a unit volume but alsosuperior in pressure resistance and self-supporting ability, and thushas been extensively used.

SUMMARY OF INVENTION

The present inventions will be detailed in sections A to G below andinclude a combination of two or more inventions described in thesections. The background and the problems for the inventions disclosedin each section will be described in each section.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the measurement results for Example 1 and ComparativeExample 2 in section A.

FIG. 2 shows the measurement results for Examples 1 and 2 in section A.

FIG. 3(A) schematically shows an example of a gas separation membranemodule.

FIG. 3(B) schematically shows an example of a gas separation membranemodule.

FIG. 4(A) schematically shows a process for manufacturing a tube sheetof a membrane module for separating a mixture of gasses.

FIG. 4(B) schematically shows this state.

FIG. 4(C) schematically shows the state where the casting resincomposition has been injected.

FIG. 5 is a cross-sectional view schematically showing a basicconfiguration of a separation membrane module of the first embodiment insection C.

FIG. 6(A) shows an exemplary structure of a module end.

FIG. 6(B) shows a conventional structure.

FIG. 7 is a view of another structure near the tube sheet.

FIGS. 8(A) and 8(B) shows an exemplary structure of a module endaccording to the second embodiment in section C; FIGS. 8(A) and 8(B)show the states at normal temperature and an elevated temperature,respectively.

FIG. 9 shows an exemplary structure of a module end according to thethird embodiment in section C.

FIG. 10(A) is a view of another exemplary embodiment, and FIG. 10(B) isa view of another exemplary embodiment.

FIG. 11(A) is a cross-sectional view showing a further exemplaryseparation membrane module.

FIG. 11(B) is an enlarged partial view of FIG. 11(A).

FIG. 12 is a view showing an exemplary arrangement of the O-RING.

FIG. 13 is a cross-sectional view of a gas separation membrane moduleaccording to one embodiment in section D.

FIG. 14 is a cross-sectional view of the tubular member in the module inFIG. 13.

FIGS. 15(A) and 15(B) shows a plan view and a sectional side view of acapping member in the module in FIG. 13, FIG. 15(A) is a cross-sectionalview taken on line X-X of FIG. 15(B).

FIG. 16(A) is a schematic view of a capping member for illustrating anexample in which the number of fixing rods is three, in accordance withan embodiment of the disclosure.

FIG. 16(B) is a schematic view of a capping member for illustrating anexample in which the number of fixing rods is four, in accordance withan embodiment of the disclosure.

FIG. 16(C) is a schematic view of a capping member for illustrating anexample in which the number of fixing rods is eight, in accordance withan embodiment of the disclosure.

FIG. 17 is a cross-sectional view schematically showing a basicconfiguration of a gas separation membrane module according to oneembodiment in section E.

FIG. 18 is an enlarged partial view of FIG. 17.

FIG. 19 is a cross-sectional view showing an exemplary casing in themodule in FIG. 17.

FIG. 20 is a cross-sectional view schematically illustrating a basicconfiguration of a gas separation membrane module according to oneembodiment in section F.

FIG. 21(A) is an enlarged partial view of FIG. 20.

FIG. 21(B) is an enlarged view further showing a part of the figure.

FIG. 22(A) is a cross-sectional view showing a gas separation membranemodule according to another embodiment.

FIG. 22(B) is an enlarged partial view.

FIG. 23 is a cross-sectional view showing a gas separation membranemodule according to a further embodiment.

FIG. 24 is a cross-sectional view showing a gas separation membranemodule according to another embodiment.

FIG. 25 is a cross-sectional view schematically showing a basicconfiguration of a gas separation membrane module according to oneembodiment in section G.

FIG. 26 is an enlarged partial view of FIG. 25.

FIG. 27 is a cross-sectional view taken on line A-A of FIG. 26.

DETAILED DESCRIPTION

There will be described embodiments of the present inventions insections A to G.

Section A: A Process for Producing Nitrogen-Rich Air from HighTemperature Gas

(Background Art)

Some aircrafts use an on-board inert-gas generating system (OBIGGS) asone of methods for protecting against explosion of a fuel tank. Anoxygen concentration of a gas-phase region in a fuel tank should belower than a given concentration for avoiding risk of explosion. Thus,an OBIGGS separates oxygen from the air to generate nitrogen-rich aircontaining nitrogen in a higher level, which is then fed to a fuel tank

An OBIGGS generates nitrogen-rich air using, for example, an airseparation membrane module. Since a treated amount of an air separationmembrane generally increases at a higher pressure and a highertemperature of a feed gas, an extracted gas from an engine, an ambientair or the like is compressed by, for example, a compressor and then fedto an air separation membrane module. The compressed gas is generallyheated to 149 to 260° C.

A conventional air separation membrane module efficiently operates at atemperature of about 82° C. to about 93° C. It cannot be, therefore,used at a high temperature as described above due to significantdeterioration in separation performance. Therefore, a compressed gas isgenerally cooled to the above temperature range by using a heatexchanger or mixing the gas with a cool air and then fed to an airseparation membrane module (see Japanese laid-open patent publicationNo. 2010-142801).

Problems to be Solved by the Invention in Section A

An objective of the invention in section A is to provide a process forproducing nitrogen-rich air by feeding a compressed air at 150° C. orhigher to an air separation membrane module.

The summary of the main invention disclosed in this section is asfollows.

[1] A process for producing nitrogen-rich air from the air using an airseparation membrane module, comprising feeding the air at 150° C. orhigher to an air separation membrane module.

Effect of the invention in section A

According to a process of the invention in section A, a nitrogen-richair containing a higher concentration of nitrogen can be produced byfeeding the air at a high temperature, for example, 150° C. or higher toan air separation membrane module. The invention of this section ischaracterized in the use of an air separation membrane with a higheroxygen-gas permeation rate and higher selectivity of oxygen and nitrogenat a high temperature, which can maintain its performance even after along period of use at a high temperature. The invention of this sectionis suitable for, for example, an explosion-proof system for a fuel tankin an aircraft. The use of the invention of this section in theexplosion-proof system allows for weight reduction of for example, aheat exchanger for cooling a hot air during feeding the air to an airseparation membrane module. Furthermore, a permeation rate of an airseparation membrane becomes higher as a temperature of a feed air ishigher, and therefore, the process of the invention of this section,which can treat a high temperature air, can be efficient with a smallermembrane area. Thus, equipments in an aircraft can be simplified and bemade lighter.

Embodiments in Section A

The invention disclosed in this section is a process for producingnitrogen-rich air from the air using an air separation membrane module,comprising feeding the air at a high temperature of 150° C. or higher tothe air separation membrane module. Unless otherwise indicated, the term“high temperature” as used herein means a temperature of 150° C. orhigher, preferably 175° C. or higher, more preferably 200° C. or higher.

An air separation membrane module can be produced by, for example,bundling 100 to 1,000,000 hollow fiber membranes with a proper length,fixing both ends of the hollow fiber bundle by a tube sheet made of, forexample, a thermosetting resin keeping at least one end of the hollowfiber open, and mounting a resulting hollow fiber membrane elementcomprising the hollow fiber bundle and the tube sheet in a vesselequipped with at least an air inlet, a permeate gas outlet and anon-permeate gas outlet in such a way that the space leading to theinside of the hollow fiber membranes and the space leading to theoutside of the hollow fiber membranes are isolated each other. In suchan air separation membrane module, gas separation is performed byfeeding the air to the space leading to the inside or the outside of thehollow fiber membranes from the air inlet and flowing in contact withthe hollow fiber membranes while oxygen in the air selectively permeatesthe membrane so that a permeate gas (oxygen-rich air) and non-permeategas (nitrogen-rich air) are discharged from the permeate gas outlet andthe non-permeate gas outlet, respectively.

An example of an air separation membrane is, but not limited to, anasymmetric air separation membrane which has an asymmetric structureconsisting of a very thin dense layer (preferably thickness: 0.001 to 5μm) mainly responsible for air separation performance and a relativelythicker porous layer (preferably thickness: 10 to to 2000 μm) supportingthe dense layer. It is preferably a hollow fiber membrane having aninner diameter of about 10 to 3000 μm and an outer diameter of about 30to 7000 μm.

The air separation membrane preferably has the following properties at ahigh temperature.

An air separation membrane preferably has a high oxygen-gas permeationrate at a high temperature. For example, it has an oxygen permeationrate (P′_(O2)) of 20×10⁻⁵ cm³(STP)/cm²·sec·cmHg or more, preferably25×10⁻⁵ cm³(STP)/cm²·sec·cmHg or more, more preferably 30×10⁻⁵cm³(STP)/cm²·sec·cmHg or more at 175° C. Furthermore, an air separationmembrane preferably exhibits high separation performance even at a hightemperature; for example, a ratio of an oxygen-gas permeation rate to anitrogen-gas permeation rate (P′_(O2)/P′_(N2)) as an index of separationperformance of a membrane is for example 1.8 or more, preferably 2.0 ormore, more preferably 2.5 or more at 175° C. A ratio of permeation ratesis generally larger at a lower temperature. A higher ratio of permeationrates, that is, higher separation performance leads to a higher recoveryratio of desired nitrogen-rich air.

Furthermore, it is preferable that in an air separation membrane, anoxygen-gas permeation rate or separation performance of the membrane isnot reduced very much even after a long period of use at a hightemperature. For example, after the use at 175° C. for 140 hours, anoxygen permeation rate (P′_(O2)) and a ratio of an oxygen-gas permeationrate to a nitrogen-gas permeation rate (P′_(O2)/P′_(N2)) are preferably75% or more, more preferably 80% or more, further preferably 90% ormore, to P′_(O2) and P′_(O2)/P′_(N2) before use, respectively.

Furthermore, an air separation membrane preferably retains its shapeeven at a high temperature as much as its functions are notdeteriorated. For example, it is preferable that a material constitutingan air separation membrane has a glass-transition temperature (Tg) ofpreferably 225° C. or higher (that is, not less than 225° C.), morepreferably 250° C. or more, further preferably 300° C. or more(including a material whose glass-transition temperature cannot bedetermined). Furthermore, it preferably retains its shape at a hightemperature for a long period; a shape retention ratio is preferably 95%or more, more preferably 99% or more after being placed at 175° C. for 2hours. Here, a shape retention ratio in this section ratio in thissection is calculated by dividing a length of a fiber after heating at175° C. for 2 hours by an initial length before heating, and convertingthe value to percentage.

Examples of a material having a glass-transition temperature of higherthan 225° C., which is suitable for a separation membrane, includepolyimides, polyether sulfones, polyamides and polyether ether ketones,particularly preferably, polyimides.

As a non-limiting material for an asymmetric gas separation hollow fibermembrane (hereinafter, sometimes simply referred to as a hollow fibermembrane), an exemplary composition of a polyimide will be described,which is suitable for an air separation membrane and has aglass-transition temperature of higher than 225° C. A polyimide having acomposition described below is an aromatic polyimide having a repeatingunit represented by general formula (1) and has a glass-transitiontemperature of generally 250° C. or higher, preferably 300° C. or higher(including a material whose glass-transition temperature cannot bedetermined).

In this formula, B is a tetravalent unit derived from a tetracarboxylicacid component, and A is a divalent unit derived from a diaminecomponent. The units constituting the aromatic polyimide will bedetailed below.

Unit B is a tetravalent unit derived from a tetracarboxylic acidcomponent, which comprises 10 to 70 mol %, preferably 20 to 60 mol % ofunit B1 having a diphenylhexafluoropropane structure represented bygeneral formula (B1) described below, and 90 to 30 mol %, preferably 80to 40 mol % of unit B2 having a biphenyl structure represented bygeneral formula (32) described below, and it is preferably substantiallycomprised of unit B1 and unit B2. If the diphenylhexafluoropropanestructure is less than 10 mol % and the biphenyl structure is more than90 mol %, gas separation performance of a polyimide obtained is sodeteriorated that a high performance gas separation membrane cannot beobtained. If the diphenylhexafluoropropane structure is more than 70 mol% and the biphenyl structure is less than 30 mol %, mechanical strengthof a polyimide obtained may be deteriorated.

Unit B can comprise a tetravalent unit based on a phenyl structurerepresented by general formula (B3). The tetravalent unit based on thephenyl structure represented by general formula (B3) is suitablycomprised in 0 to 30 mol %, preferably 10 to 20 mol %.

Furthermore, unit B can comprise a tetravalent unit B4 derived fromanother tetracarboxylic acid other than units B1, B2 and B3.

Unit A is a divalent unit derived from a diamine component, andcomprises unit A1 selected from the group consisting of general formulas(A1a), (A1b) and (A1c) and unit A2 selected from the group consisting ofgeneral formulas (A2a) and (A2b). Furthermore, unit A can comprise adivalent unit A3 derived from another diamine component other than unitsA1 and A2.

Unit A1a is a divalent unit based on a biphenyl structure represented byFormula (A1a), and unit A1b and A1c comprise hexafluorinated structuresrepresented by Formulas (A1b) and (A1c), respectively, more specificallya unit having a structure comprising two trifluoromethyl groups.

wherein X is chlorine or bromine, and n is 1 to 3.

wherein r is 0 or 1, and the phenyl rings can be substituted by OHgroup.

wherein Y represents O or a single bond.

When unit A1 comprises the unit represented by Formula (A1a), it issuitably comprised in 30 to 70 mol %, preferably 30 to 60 mol % in unitA. The benzidines contribute to improvement permselectivity. If theamount thereof is too much, a resulting polymer becomes insoluble and itis difficult to form a membrane, while if the amount is too low, apermselectivity is disadvantageously reduced.

When unit A1 contains the units represented by Formulas (A1b) and/or(A1c), these are comprised in 10 to 50 mol %, preferably 20 to 40 mol %in unit A.

Unit A2 is a sulfur-containing heterocyclic structure, specificallyselected from the units represented by general formulas (A2a) and (A2b).

wherein R and R′ are hydrogen or an organic group, and n is 0, 1 or 2.

wherein R and R′ are hydrogen or an organic group, and X is —CH₂— or—CO—.

Unit A2 is comprised in 90 to 30 mol %, preferably 90 to 40 mol %, morepreferably 90 to 50 mol %, further preferably 80 to 60 mol % in unit A.

Unit A3 can be comprised in 50 mol % or less, preferably 40 mol % orless, more preferably 20 mol % or less in unit A.

There will be described a monomer component constituting each of theabove units in an aromatic polyimide.

The unit having the diphenylhexafluoropropane structure represented bygeneral formula (B1) can be prepared using a(hexafluoroisopropylidene)diphthalic acid, its dianhydride or its esteras a tetracarboxylic acid component. The(hexafluoroisopropylidene)diphthalic acids can be suitably selected from4,4′-(hexafluoroisopropylidene)diphthalic acid,3,3′-(hexafluoroisopropylidene)diphthalic acid,3,4′-(hexafluoroisopropylidene)diphthalic acid, their dianhydrides andtheir esters, particularly suitably4,4′-hexafluoroisopropylidene)diphthalic acid, its dianhydride and itsester.

The unit having the biphenyl structure represented by general formula(B2) can be prepared by using biphenyltetracarboxylic acids such asbiphenyltetracarboxylic acid, its dianhydride and its ester as atetracarboxylic acid component. The biphenyltetracarboxylic acids can besuitably selected from 3,3′,4,4′-biphenyltetracarboxlic acid,2,3,3′,4′-biphenyltetracarboxlic acid, 2,2′,3,3′-biphenyltetracarboxylicacid, their dianhydrides and their esters, particularly suitably3,3′,4,4′-biphenyltetracarboxylic acid, its dianhydride and its ester.

The tetravalent unit based on a phenyl structure represented by generalformula (B3) can be formed by using pyromellitic acids such aspyromellitic acid and its anhydride. The pyromellitic acids are suitablefor improving mechanical properties. If its amount is excessive, it isdifficult to form a hollow fiber membrane because a polymer solutionbecomes unstable, for example, it is coagulated during membraneformation.

Another tetracarboxylic acid component giving unit B4 is atetracarboxylic acid other than those described above, and can beselected from those which can sometimes further improve performancewithout deteriorating the effects of the invention in this section.Examples can include diphenyl ether tetracarboxylic acids, benzophenonetetracarboxylic acids, diphenylsulfonetetracarboxylic acids, naphthalenetetracarboxylic acids, diphenyl methanetetracarboxylic acids anddiphenylpropane tetracarboxylic acids.

The divalent unit based on the biphenyl structure represented by generalformula (A1a) can be formed by using halogenated benzidines representedby general formula (A1a-M) as a diamine component.

wherein X is chlorine or bromine, and n===1 to 3.

Examples of halogenated benzidines include dichlorobenzidines(diaminodichlorobiphenyls), tetrachlorobenzidines(diaminotetrachlorobiphenyls), hexachlorobenzidines,tetrabromobenzidines, dibromobenzidines and hexabromobenzidines. Anexample of dichlorobenzidines can include 3,3-dichlorobenzidine (DCB)and an example of tetrachlorobenzidines can include2,2′,5,5′-tetrachlorobenzidine (TCB).

The divalent unit represented by general formula (A1b) is formed byusing a hexafluorinated compound represented by general formula (A1b-M)as a diamine component.

wherein r is 0 or 1, and the phenyl rings may be substituted by OHgroup.

A preferable hexafluorinated compound represented by (A1b-M) isrepresented by any of general formulas (A1b-M1) to (A1b-M3).

The bis[(aminophenoxy)phenyl]hexafluoropropanes represented by generalformula (A1b-M1) can include for example,2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane or2,2-bis[4-(3-aminophenoxy)phenyl]hexafluoropropane. Thebis(aminophenyl)hexafluoropropanes represented by general formula(A1b-M2) can include, for example,2,2-bis(4-aminophenyl)hexafluoropropane. The hydroxylatedbis(aminophenyl)hexafluoropropanes represented by general formula(A1b-M3) can include, for example,2,2-bis(3-amino-4-hydroxy)hexafluoropropane.

The divalent unit represented by general formula (A1c) can be preparedby using a hexafluorinated compound represented by general formula(A1c-M) as a diamine component.

wherein Y represents O or a single bond.

The diamine compounds represented by general formula (A1c-M) caninclude, for example, 2,2′-bis(trifluoromethyl)-4,4′-diaminodiphenylether and 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl.

The unit having a structure represented by general formula (A2a) or(A2b) can be prepared by using an aromatic diamine represented bygeneral formula (A2a-M) or (A2b-M), respectively, as a diaminecomponent.

wherein R and R′ are hydrogen or an organic group, and n is 0, 1 or 2.

wherein R and R′ are hydrogen or an organic group.

The aromatic diamine represented by general formula (A2a-M) can includesuitably the diaminodibenzothiophenes represented by general formula(A2a-M1), that is, general formula (A2a-M) in which n is 0, or thediaminodibenzothiophene=5,5-dioxides represented by general formula(A2a-M2), that is, general formula (A2a-M) in which n is 2.

wherein R and R′ are hydrogen or an organic group.

wherein R and R′ is hydrogen or an organic group.

The diaminodibenzothiophenes (general formula (A2a-M1)) can include, forexample, 3,7-diamino-2,8-dimethyldibenzothiophene,3,7-diamino-2,6-dimethyldibenzothiophene,3,7-diamino-4,6-dimethyldibenzothiophene,2,8-diamino-3,7-dimethyldibenzothiophene,3,7-diamino-2,8-diethyldibenzothiophene,3,7-diamino-2,6-diethyldibenzothiophene,3,7-diamino-4,6-diethyldibenzothiophene,3,7-diamino-2,8-dipropyldibenzothiophene,3,7-diamino-2,6-dipropyldibenzothiophene,3,7-diamino-4,6-dipropyldibenzothiophene,3,7-diamino-2,8-dimethoxydibenzothiophene,3,7-diamino-2,6-dimethoxydibenzothiophene, and3,7-diamino-4,6-dimethoxydibenzothiophene.

The diaminodibenzothiophene=5,5-dioxides (general formula (A2a-M2)) caninclude, for example,3,7-diamino-2,8-dimethyldibenzothiophene=5,5-dioxide,3,7-diamino-2,6-dimethyldibenzothiophene=5,5-dioxide,3,7-diamino-4,6-dimethyldibenzothiophene=5,5-dioxide,2,8-diamino-3,7-dimethyldibenzothiophene=5,5-dioxide,3,7-diamino-2,8-diethyldibenzothiophene=5,5-dioxide,3,7-diamino-2,6-diethyldibenzothiophene=5,5-dioxide,3,7-diamino-4,6-diethyldibenzothiophene=5,5-dioxide,3,7-diamino-2,8-dipropyldibenzothiophene=5,5-dioxide,3,7-diamino-2,6-dipropyldibenzothiophene=5,5-dioxide,3,7-diamino-4,6-dipropyldibenzothiophene=5,5-dioxide,3,7-diamino-2,8-dimethoxydibenzothiophene=5,5-dioxide,3,7-diamino-2,6-dimethoxydibenzothiophene=5,5-dioxide, and3,7-diamino-4,6-dimethoxydibenzothiophene=5,5-dioxide.

The diaminothioxanthene-10,10-diones that are given by selecting —CH₂—as X in the general formula (A2b-M) can include, for example,3,6-diaminothioxanthene-10,10-dione,2,7-diaminothioxanthene-10,10-dione,3,6-diamino-2,7-diethylthioxanthene-10,10-dione,3,6-diamino-2,8-diethylthioxanthene-10,10-dione,3,6-diamino-2,8-dipropyithioxanthene-10,10-dione, and3,6-diamino-2,8-dimethoxythioxanthene-10,10-dione.

The diaminothioxanthene-9, 10, 10-triones that are given by selecting—CO— as X in the general formula (A2b-M) can include, for example,3,6-diamino-thioxanthene-9, 10,10-trione and 2,7-diamino-thioxanthene-9,10,10-trione.

Another diamine component giving unit A3 is a diamine compound otherthan those described above, and selected from compounds which cansometimes further improve performance without deteriorating the effectsof the invention in this section.

Examples can include:

diaminodiphenyl sulfones such as 3,3′-diaminodiphenyl sulfone,3,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfone,4,4′-diamino-3,3′-dimethyldiphenyl sulfone;

diaminodiphenyl ethers such as 4,4′-diaminodiphenyl ether,3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether,3,3′-dimethyl-4,4′-diaminodiphenyl ether and3,3′-diethoxy-4,4′-diaminodiphenyl ether;

diaminodiphenyl methanes such as 4,4′-diaminodiphenyl methane and3,3′-diaminodiphenyl methane;

2,2-bis(aminophenyl)propanes such as 2,2-bis(3-aminophenyl)propane and2,2-bis(4-aminophenyl)propane;

2,2-bis(aminophenoxyphenyl)propanes such as2,2-bis[4-(4-aminophenoxy)phenyl]propane and2,2-bis[4-(3-aminophenoxy)phenyl]propane;

diaminobenzophenones such as 4,4′-diaminobenzophenone and3,3′-diaminobenzophenone;

diaminobenzoic acids such as 3,5-diaminobenzoic acid;

phenylenediamines such as 1,3-phenylenediamine and 1,4-phenyl

dichlorodiaminodiphenyl ethers such as2,2′-dichloro-4,4′-diaminodiphenyl ether;

tolidines such as ortho-tolidine and meta-tolidine; and

dihydroxydiaminobiphenyls such as 2,2′-dihydroxy-4,4′-diaminobiphenyl.

Among these, preferred are diaminodiphenyl sulfones, diaminodiphenylethers, diaminobenzoic acids, dichlorodiaminodiphenyl ethers anddihydroxydiaminobiphenyls.

When an aromatic polyimide represented by a repeating unit of generalformula (1) is used for an asymmetric air separation membrane, forexample, it is preferable that the tetracarboxylic acid component is acombination of 4,4′-(hexafluoroisopropylidene-bis(phthalic anhydride) asa carboxylic acid giving unit B1, 3,3′,4,4-biphenyl tetracarboxylicdianhydride as a carboxylic acid giving unit B32 and pyromelliticdianhydride as a carboxylic acid giving unit B3, and the diaminecomponent is a combination of 2,2′,5,5′-tetrachlorobenzidine as adiamine giving unit A1 and3,7-diamino-dimethyldibenzothiophene=5,5-dioxide as a diamine givingunit A2. 3,7-Diamino-dimethyldibenzothiophene=5,5-dioxide means amixture of 3,7-diamino-2,8-dimethyldibenzothiophene=5,5-dioxide as amain component containing isomers in which a methyl group is attached ata different position, that is,3,7-diamino-2,6-dimethyldibenzothiophene=5,5-dioxide and3,7-diamino-4,6-dimethyldibenzothiophene=5,5-dioxide.

The aromatic polyimide solution can be suitably prepared by a two-stepprocess of combining a tetracarboxylic acid component and a diaminecomponent in an organic polar solvent in a given composition ratio,which is then polymerized at a low temperature of around roomtemperature to form a polyamide acid, and of then imidizing thepolyamide acid by heating or chemically imidizing by adding, forexample, pyridine, or alternatively, a one-step process of combining atetracarboxylic acid component and a diamine component in an organicpolar solvent in a given composition ratio, which is then polymerizedand imidized at a high temperature of about 100 to 250° C., preferablyabout 130 to 200° C. hi imidizing by heating, the reaction is suitablyconducted while water or an alcohol generated is removed. An amount usedof the tetracarboxylic acid component and the diamine component to theorganic polar solvent is suitably such that a concentration of thepolyimide in the solvent is about 5 to 50% by weight, preferably 5 to40% by weight.

The aromatic polyimide solution prepared after the polymerization andthe imidizing can be directly used in spinning. Alternatively, forexample, the aromatic polyimide solution obtained is added to a solventin which the aromatic polyimide is insoluble, to precipitate and isolatethe aromatic polyimnide, which is then dissolved in an organic polarsolvent to a given concentration to prepare an aromatic polyimidesolution which can be used in spinning.

In the aromatic polyimide solution used in the spinning, a concentrationof the polyimide is preferably 5 to 40% by weight, further preferably 8to 25% by weight, and a solution viscosity (rotational viscosity) is 100to 15000 poise, preferably 200 to 10000 poise, particularly preferably300 to 5000 poise at 100° C. If a solution viscosity is less than 100poise, a uniform membrane (film) may be formed, but an asymmetricmembrane with a large mechanical strength cannot be obtained. If it ismore than 15000 poise, extrusion from a spinning nozzle becomesdifficult, so that an asymmetric hollow fiber membrane having a desiredshape cannot be obtained.

There are no particular restrictions to the organic polar solvent aslong as it can suitably dissolve an aromatic polyimide obtained, andexamples of such a solvent include phenols such as phenol, cresol andxylenol; catechols such as catechol and resorcin in which a benzene ringdirectly has two hydroxyl groups; phenolic solvents includinghalogenated phenols such as 3-chlorophenol, 4-chlorophenol (equivalentto parachlorophenol described later), 3-bromophenol, 4-bromophenol and2-chloro-5-hydroxytoluene; or amide solvent including amides such asN-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone,N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylactamide andN,N-diethylacetamide; or mixtures of these.

A hollow fiber membrane can be suitably prepared by spinning in adry/wet manner (dry-wet spinning) using the above aromatic polymidesolution. The dry-wet manner is a method where a solvent in the surfaceof the polymer solution having a hollow fiber shape is evaporated toform a thin dense layer (separation layer) and immersing the polymersolution in a coagulation liquid (a solvent which is compatible with thesolvent in the polymer solution and in which a polymer is insoluble) tocause phase separation which is then utilized to form pores, giving aporous layer (supporting layer) (a phase inversion method), and has beenproposed by Loeb et al. (for example, U.S. Pat. No. 3,133,132).

A dry-wet spinning manner is a method for forming a hollow fibermembrane using a spinning nozzle in a dry/wet manner, which is describedin, for example, Japanese laid-open patent publication Nos. 1986-133106and 1991-267130.

The production process generally has the steps of spinning(spinning-dope extruding), coagulating, washing, drying and heating.

First, in the spinning (spinning-do extruding step), a spinning nozzleused for extruding a spinning dope solution can be any nozzle capable ofextruding the spinning dope solution as a hollow fiber form, suitably atube-in-orifice type nozzle and the like. Generally, a temperature rangeof the aromatic polyimide solution during extrusion is preferable about20° C. to 150° C., particularly 30° C. to 120° C. A suitable temperaturerange depends on a kind of a solvent for the dope and its viscosity.Furthermore, spinning is conducted while a gas or liquid is fed into theinside of the hollow fiber form extruded from the nozzle.

In the coagulating step subsequent to the spinning step, the hollowfiber form discharged from a nozzle is extruded into the air or an inertgas atmosphere such as nitrogen, and then fed to a coagulation bath forimmersion in a coagulation liquid Suitably, a coagulation liquid.Suitably, a coagulation liquid is substantially unable to dissolve anaromatic polyimide component while being compatible with a solvent inthe aromatic polyimide solution. Suitable examples include, but notlimited to, water; lower alcohols such as methanol, ethanol and propylalcohol; ketones having a lower alkyl group such as acetone, diethylketone and methyl ethyl ketone; and their mixtures. When the solvent inthe aromatic polyimide solution is an amide solvent, an aqueous solutionof the amide solvent, an aqueous solution of the amide solvent is alsopreferable.

In the next washing step, if necessary, the hollow fiber is washed witha washing solvent such as ethanol, and then the coagulation liquidand/or the washing solvent in the outside and the inside of the hollowfiber are replaced with a replacing solvent including an aliphatichydrocarbon such as isopentane, n-hexane, isooctane and n-heptane.

In the subsequent drying step, the hollow fiber including the replacingsolvent is dried at a proper temperature. Then, in the heating step, thefiber is heated preferably at a temperature lower than a softening pointor second-order transition point of the aromatic polyimide used, to givean asymmetric gas separation hollow fiber membrane.

INDUSTRIAL USABILITY

In accordance with the invention of this section, nitrogen-rich aircontaining a higher concentration of nitrogen can be obtained by feedingthe air at a high temperature, for example, 150° C. or more to an airseparation membrane module. A process according to the invention in thissection can be used, for example, for an explosion-proof system in afuel tank in an aircraft.

The inventions according to section A are as follows.

[1] A process for producing nitrogen-rich air using an air separationmembrane module, comprising feeding the air at 150° C. or higher to theair separation membrane module.

[2] The process according [1], wherein for the air separation membranemodule, at the initiation of the use, an oxygen-gas permeation rateP′_(O2)) at 175° C. is 20×10⁻⁵ cm³(STP)/cm²·sec·cmHg or more and a ratioof an oxygen-gas permeation rate to a nitrogen-gas permeation rate(P′_(O2)/P′_(N2)) at 175° C. is 1.8 or more; and

after the use at 175° C. for 140 hours, P′_(O2) and P′_(O2)/P′_(N2) areretained in levels of 90% or more of P′_(O2) and P′_(O2)/P′_(N2) beforethe initiation of the use, respectively.

[3] The process as described in [1] or [2], wherein an air separationmembrane in the air separation membrane module comprises a materialhaving no glass-transition temperatures at 225° C. or lower.

[4] The process according to any one of [1] to [3], wherein after beingplaced at 175° C. for 2 hours, the air separation membrane exhibits ashape-retention ratio of 95% or more.

[5] A method for explosion protection of an aircraft, comprisingproducing nitrogen-rich air by the production process according to anyone of [1] to [4], and feeding the nitrogen-rich air to a fuel tank foran aircraft.

Section B: a gas separation membrane module having adequate heatresistance and pressure resistance at a high temperature and a highpressure without being cracked

Technical Field

The invention of this section relates to a gas separation membranemodule for mixed-gas separation in which a fiber bundle consisting of anumber of hollow fiber membranes exhibiting selective permeability isfixed together to a tube sheet manufactured by curing a particular epoxycomposition.

Background Art

A hollow-fiber type gas separation membrane module has a fiber bundleconsisting of a number of hollow-fiber membranes exhibiting selectivepermeability, at least one end of which is fixed together to a plate(tube sheet) of a cured resin of cast molding, and the fiber bundle ishoused in a casing comprising at least a mixed gas inlet, a permeate gasoutlet and a non-permeate gas outlet. Besides functioning to fix thefiber bundle together, the tube sheet has another function to isolatethe internal space of the hollow fiber membrane from its external space,and to retain gas tightness of the internal space and external space bysealing between the hollow fibers and between the hollow fibers and thecasing. The hollow-fiber type gas separation membrane module would failto perform suitable separation if gas-tightness by the tube sheet islost.

In a gas separation method using a separation membrane, suitable gasseparation can be sometimes achieved by feeding a mixed gas at a hightemperature and a high pressure. In such cases, a material for a tubesheet is required to exhibit higher heat resistance and pressureresistance and its glass-transition temperature or heat deflectiontemperature must be higher by at least several dozens of degreescentigrade than an operation temperature of the gas separation membranemodule.

A thermosetting resin is generally used as a tube sheet material forachieving higher heat resistance and pressure resistance, which isheated at a considerably high temperature during tube sheet formationfor completing curing of the thermosetting resin. If a tube sheetprepared by incomplete curing is used, the curing reaction proceedsduring operating a separation membrane module at a high temperature andthe tube sheet is shrunk, which causes inadequate sealing between thetube sheet and the casing. The tube sheet material must be, therefore,heat-resistant to a considerably high temperature during the tube sheetformation.

As a gas separation membrane module which can be used for separation ofa mixed gas at a high temperature and a high pressure, for example,Japanese laid-open patent publication No. 1987-74434 has described ahollow fiber element produced using a denatured epoxy resin prepared byreacting a phenol-novolac type epoxy resin with a liquid polybutadienehaving a reactive terminal functional group.

Problems to be Solved by the Invention in Section B

However, a conventional tube sheet material is subjected to much cureshrinkage during a tube sheet formation, which causes problems such ascracks and breakage of the tube sheet. Furthermore, when a priority isgiven to only pressure resistance and heat resistance, there may beproblems such as crack forming and breakage of the tube sheet underimpact during operation because a flexibility of the tube sheet materialis poor. An objective of the invention of this section is to provide atube sheet f a tube sheet for a gas separation membrane module retainingadequate heat resistance and pressure resistance under a hightemperature and a high pressure without being cracked.

The summary of the main invention disclosed in this section is asfollows.

[1] A gas separation membrane module comprising

a fiber bundle consisting of a number of hollow fiber membranes havinggas separation performance;

a casing having a mixed gas inlet, a permeate gas outlet and anon-permeate gas outlet, in which the hollow fiber bundle is placed; and

a tube sheet fixing at least one end of the hollow fiber bundle;

wherein the tube sheet is formed by an epoxy cured material prepared bycuring a casting resin composition containing

a denatured epoxy resin formed by reacting (a) a phenol novolac typeepoxy compound and (b) a butadiene-acrylonitrile copolymer having aterminal functional group capable of reacting with an epoxy group, and

(c) a hardener.

Advantages of the Invention in Section B

Since a tube sheet in a gas separation membrane module according to theinvention of this section is produced using a butadiene-acrylonitrilecopolymer having a terminal functional group capable of reacting with anepoxy group, it is more flexible than a conventional tube sheet.Furthermore, when it is exposed to a high-temperature and high-pressuregas during forming a tube sheet or operating a gas separation membranemodule, the tube sheet is not cracked and its adhesiveness to a hollowfiber or sealing between the tube sheet and a casing is notdeteriorated.

Embodiments in Section B

An epoxy cured material forming a tube sheet in a hollow fiber elementaccording to the invention of this section can be produced by heatcuring a casting resin composition containing at least

a denatured epoxy resin formed by reacting (a) a phenol novolac typeepoxy compound and (b) a butadiene-acrylonitrile copolymer having aterminal functional group capable of reacting with an epoxy group, and

(c) a hardener.

This will be detailed below.

Denatured Epoxy Resin

A denatured epoxy resin can be obtained by reacting a phenol novolactype epoxy compound (hereinafter, sometimes referred to as epoxycompound (a)) with a butadiene-acrylonitrile copolymer having a terminalfunctional group capable of reacting with an epoxy group (hereinafter,sometimes referred to as compound (b)).

A phenol novolac type epoxy compound (a) used in the invention of thissection is a compound represented by general formula (a):

wherein R″ represents alkyl having 1 to 3 carbon atoms or hydrogen; andn represents an integer of 0 to 500, preferably 0 to 20.

In Formula (a), R″ is preferably methyl or hydrogen. The epoxy compound(a) represented by general formula (a) preferably has a molecular weightof 300 to 2000 and an epoxy equivalent of 150 to 250. Examples of epoxycompound (a) include jERI52 and jER154 from Mitsubishi ChemicalCorporation; EPICLON-N740, N-770, N-775 and the like from DICCorporation; YDPN-638 and YDCN-700 series from Tohto Kasei Co., Ltd.;and D.E.N.438 from The Dow Chemical.

In a butadiene-acrylonitrile copolymer having a terminal functionalgroup capable of reacting with an epoxy group (compound (b)) used in theinvention of this section, examples of the functional group capable ofreacting with an epoxy group include carboxyl, amino and hydroxylgroups, particularly preferably carboxyl group. A resulting tube sheetcan be made flexible by comprising the compound (b).

The butadiene-acrylonitrile copolymer having a terminal functional groupcapable of reacting with an epoxy group is preferably acarboxyl-terminated butadiene⋅acrylonitrile copolymer (CTBN) representedby general formula (b).

In Formula (b), m represents the total number of repetition of thebutadienemonomer unit and n represents the total number of repetition ofthe acrylonitrile monomer unit, and when 2 or more of the structuresrepresented in [ ] are present, m and n represent the sum of arepetition number of each unit, respectively, and they can be present asa block or at random.

CTBN represented by general formula (b) preferably has a molecularweight of 2000 to 4000; for example, CTBN preferably contains 5 to 50%by weight of an acrylonitrile monomer unit. Examples of commerciallyavailable CTBN include Hypro™CTBN1300×8, CTBN1300×13 and CTBN1300×31from Emerald Performance Materials.

A denatured epoxy resin is produced by mixing preferably 5 to 50 partsby weight, more preferably 5 to 20 parts by weight of compound (b) with100 parts by weight of epoxy compound (a) and reacting them. The use ofa denatured epoxy resin in which the contents of these compounds arewithin the above ranges can avoid crack formation in a resulting tubesheet at a high temperature and a high pressure and there is no problemof deformation due to too lowering of a glass-transition temperature.Other compounds can be added as long as they do not adversely affect theobjectives of the invention in this section. Although there are noparticular restrictions to the reaction conditions in preparing thedenatured epoxy resin, a reaction temperature is preferably 100 to 200°C.; and a reaction time is preferably 2 to 5 hours.

Hardener

There are no particular restrictions to a hardener used in the inventionof this section as long as it is a thermosetting agent for an epoxyresin, including amines, phenols and acid anhydrides, more preferablyacid anhydrides. Examples of an acid anhydride include phthalicanhydride, pyromellitic dianhydride,methyl-5-norbornene-2,3-dicarboxylic anhydride (methylnadic anhydride)and benzophenone tetracarboxylic dianhydride, particularly preferablymethyl-5-norbornene-2,3-dicarboxylic anhydride.

Hardening Accelerator

A casting resin composition used in the invention of this section can,if necessary, contain a hardening accelerator, which can include animidazole compound. Examples of an imidazole compound include2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole,2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole,1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole and-cyanoethyl-2-ethyl-4-methylimidazole, particularly preferably2-ethyl-4-methylimidazole.

Epoxy Cured Material

An epoxy cured material forming the tube sheet in the invention of thissection can be produced by heat-curing a casting resin compositioncontaining the above denatured epoxy resin, a hardener and, ifnecessary, a hardening accelerator (hereinafter, sometimes referred toas a casting resin composition). A mixing ratio of the denatured epoxyresin to the hardener and so on in preparation of the casting resincomposition depends on the number of epoxy functional groups in thedenatured epoxy resin and the number of functional groups in thehardener and can be appropriately adjusted depending on, for example, aviscosity of the desired casting resin composition. To 100 parts byweight of the denatured epoxy resin, preferably 0 to 5 parts by weight,more preferably 0.1 to 3 parts by weight of the hardening accelerator isused.

In a heating step, for example, the casting resin composition issubjected to the first curing by heating it until the casting resincomposition does not flow, and then the resin after the first curing ispreferably post-cured at a further high temperature. In post-curing, foravoiding change in physical properties of the tube sheet material duringoperating the module, the casting resin composition is preferably heatedat a temperature equal to or higher than a temperature in the finaloperation, for example, preferably 100° C. to 250° C., more preferably120° C. or more, for 2 to 10 hours. The first curing is, for example,but not limited to, preferably less than 100° C., more preferably 50 to85° C. for 2 to 24 hours. It is preferable that the resin after thefirst curing is preferable that the resin after the first curing isheated to a post-curing temperature at a temperature-increase rate of 5°C./min or less because thermal runaway due to reaction heat rapidlygenerated in the casting resin composition can be avoided. A process forforming a tube sheet will be described later.

Gas Separation Membrane Module

There will be described a structure of a gas separation membrane moduleaccording to the invention of this section.

It is known that a gas separation membrane module made up of hollowfiber membranes is a bore feed type or a shell feed type. For example,in a bore feed type gas separation membrane module, a number of hollowfiber membranes B14 (for example, several hundred to severalhundred-thousand) are put together as a hollow fiber bundle, which ishoused in a casing B15 having at least a mixed gas inlet B11, a permeategas outlet B12 and a non-permeate gas outlet B13, and is fixed to thecasing B15 with tube sheets B16 a and B16 b formation in such a mannerthat the hollow fiber membranes B14 are open at the both ends of thehollow fiber bundle, so that a space where a gas is fed from a mixed gasinlet B11, passes through the inside of the hollow fiber membrane B14and is led to a non-permeate gas outlet B13 (non-permeate side) and aspace outside of the hollow fiber membrane B14 leading to a permeate gasoutlet B12 (permeate side) are isolated each other as shown in FIG.3(A). The casing B15 can be made of, for example, a material includingmetals such as stainless steel, plastics, fiber-reinforced plastics andceramics. In a shell feed type gas separation membrane module, forexample, as shown in FIG. 3(B), a tube sheet is formed at one end of ahollow fiber bundle in such a manner that a non-permeate side spacewhere a mixed gas is fed from a mixed gas inlet 131 and is led to anon-permeate gas outlet B13 is outside of the hollow fiber membranes B14while a permeate side space leading to the permeate gas outlet B12 isinside of the hollow fiber membranes B14.

In FIGS. 3(A) and (B), while a mixed gas fed from the mixed gas inletB11 in the gas separation membrane module flows in contact with thehollow fiber membrane B14 in the gas separation membrane module, a highpermeate gas preferentially permeates the hollow fiber membrane B14 toseparate the mixed gas into a gas rich in a high permeate gas (permeategas) and a remaining non-permeate gas poor in a high permeate gas(non-permeate gas). The permeate gas is discharged from the permeate gasoutlet B12 while the non-permeate gas is discharged from thenon-permeate gas outlet B13. Either or both of the non-permeate gas andthe permeate gas discharged from the gas separation membrane module arerecovered, depending on an application.

As a hollow fiber used in a gas separation membrane, the use of a numberof hollow fibers with a thin thickness and a small diameter ispreferable because a high membrane area and a higher separationefficiency can be conducted even in a small device, which iseconomically advantageous. For example, the hollow fiber can have, butnot limited to, a film thickness of 10 to 500 μm and an outer diameterof 50 to 2000 μm. Furthermore, a gas separation membrane can behomogeneous or heterogeneous like a composite membrane or an asymmetricmembrane, and can be microporous or nonporous.

Examples of a gas separation membrane can include those made of apolymer materials such as polyimides, polyetherimides, polyamides,polyamideimides, polysulfones, polycarbonates, silicone resins,cellulose polymers and ceramic materials such as zeolite. For example, agas separation membrane made of a polyimide is preferably an aromaticpolyimide hollow fiber separation membrane, more preferably an aromaticpolyimide asymmetric hollow fiber separation membrane.

A fiber arrangement of a hollow fiber bundle may include parallelarrangement, cross arrangement, fabric arrangement and spiralarrangement. A hollow fiber bundle can have a core tube substantially inthe center or the periphery of a hollow fiber bundle can be wrapped witha film. Furthermore, the shape of the hollow fiber bundle can becylindrical, tabular r or prismatic, and it can be put in the casing inan unchanged shape as described above, or in a folded U-shape or aspirally coiled shape.

There will be described a process for producing a gas separationmembrane module according to the invention of this section.

First, there will be described a method for putting hollow fibermembranes together as a hollow fiber bundle.

The following is an example of a method for putting together hollowfiber membranes in such a manner that that they alternately cross eachother at an angle of 5 to 30° to an axial direction. One to 100 hollowfiber membranes are arranged on a tube to be a core (core tube) by afiber-arranging guide which shuttles at a certain rate in an axialdirection of the core tube, while the core tube simultaneously rotatesat a certain rate. Thus, the hollow fiber membranes are arranged not inparallel with the axis, but at an angle corresponding to rotation of thecore tube to the axial direction. Once fiber arrangement reaches oneend, the hollow fiber membranes are fiber membranes are fixed there andthen the fiber-arranging guide moves back in the reverse direction.Since the core tube continues to rotate in the same direction, then thefibers are arranged at an angle to the axial direction which is justopposite to the above angle. This process is repeated so that hollowfiber membranes are alternately arranged on hollow fiber membranesarranged in an opposite angle to give a hollow fiber bundle.

There will be described a method for forming a tube sheet in theinvention of this section. A method for forming a tube sheet can becentrifugal molding or stationary molding, and stationary molding ispreferable because a convenient apparatus can be used and anproductivity can be increased. There will be described an example ofstationary molding.

For example, a hollow fiber bundle, which a given number of hollow fibermembranes B24 with a given length is put together by the above method,is put in a casing B22 without a core tube or with a core tube remainedsubstantially in the center. Then, it is placed in a given position in amold B21 whose end a tube sheet is to be formed, and subsequently, thehollow fiber bundle and the cylindrical casing B22 are substantiallyvertically held in such a way that the end is down. FIG. 4bschematically shows this state.

A given amount of a casting resin composition for forming a tube sheet B23 is cast into the mold B21. FIG. 4c schematically shows the statewhere the casting resin composition has been injected. Although thereare no particular restrictions to a method for casting a casting resincomposition, casting from the lower part of the mold using a syringe ispreferable because it is easy to uniformly cast the casting resincomposition in the mold B21 and between the hollow fiber membranes B24.If the casting resin composition is cast too fast, the casting resincomposition cannot be uniformly cast to the parts to be filled, andtherefore, it is preferably cast over a sufficient period. It issuitable to appropriately control a temperature of the mold B21 duringcasting the casting resin composition into the mold B21. Likewise, it issuitable to control a temperature of the casting resin composition.

The casting resin composition before curing is preferably in a liquidstate at a temperature during resin cast in the light of moldability.

There are no particular restrictions to a viscosity of the casting resincomposition, but it is preferable that a viscosity at a temperature of70 to 90° C. common n resin cast is preferably less than 120 poise,particularly preferably less than 20 poise. Here, a viscosity of theresin composition can be suitably measured using a rotating viscometer.

If a viscosity of the casting resin composition at a temperature of 70to 90° C. is 120 poise or more, there is a problem that a resin cast inmolding a tube sheet takes a long time and foams generated during resincast cannot be easily removed, and also, a space between the hollowfiber membranes are inadequately filled with the resin, which causesvoids.

After cast of the casting resin composition into the mold B21, the moldB21 and the hollow fiber bundle are kept at a certain temperature toconduct the first curing of the casting resin composition to form a tubesheet B23. In this process, a temperature is suitably less than 100° C.,preferably 50 to 85° C. An excessively high temperature in this stage isnot preferable because curing of the casting resin composition becomesso severe that strength of a tube sheet finally obtained is adverselyaffected.

After curing of the casting resin composition, it is preferable toconduct post-curing of the casting resin composition by heating in thelight of improving durability and mechanical properties. A temperatureduring the post-curing is preferably 100° C. to 250° C. A temperature oflower than 100° C. during post-curing is not preferable because thecasting resin casting resin composition is inadequately cured.Furthermore, an excessively high temperature during post-curing is notpreferable because curing of the casting resin composition becomes sosevere that a problem about a strength of a tube sheet occurs. Inpost-curing of the casting resin composition, the composition can beheated at different temperatures in multiple steps.

After post-curing of the casting resin composition, the tube sheet iscut to open the ends of the hollow fiber membranes, giving a hollowfiber element in which the ends of the hollow fibers are kept open andfixed to the tube sheet.

Here, in case of forming a tube sheet at both ends of the hollow fiberbundle, after a tube sheet is formed at one end of the hollow fiberbundle as described above, then a tube sheet is formed at the other endby a similar procedure. “After a tube sheet is formed at one end” may be“after the hollow fiber membranes are made open by cutting the tubesheet”. Alternatively, it is also suitable that one end is placed withinthe mold, the casting resin composition is cast and subjected to thefirst curing and then a tube sheet is formed at the other end beforepost-curing, and both ends can be processed by the procedure after thepost-curing at the same time.

For a method for separating a mixed gas using a separation membranemodule according to the invention of this section, there are noparticular restrictions to a mixed gas to be separated as long as it isa mixed gas of two or more components. A gas separation membrane moduleaccording to the invention of this section can be suitably used for, forexample, separation of nitrogen-rich air and oxygen-rich air from theair, separation of hydrogen gas from a hydrogen-containing mixed gas andseparation of water vapor from a mixed vapor of water vapor and anorganic vapor (dehydration of an organic vapor).

The inventions according to section B are as follows.

[1] A gas separation membrane module comprising

a fiber bundle consisting of a number of hollow fiber membranes havinggas separation performance;

a casing having a mixed gas inlet, a permeate gas outlet and anon-permeate gas outlet, within which the hollow fiber bundle is placed;and

a tube sheet fixing at least one end of the hollow fiber bundle;

wherein the tube sheet is formed by an epoxy cured material prepared bycuring a casting resin composition containing

a denatured epoxy resin formed by reacting (a) a phenol novolac typeepoxy compound and (b) a butadiene-acrylonitrile copolymer having aterminal functional group capable of reacting with an epoxy group, and

(c) a hardener.

[2] The gas separation membrane module according to [1], wherein thecasting resin composition further contains a curing accelerator.

[3] The gas separation membrane module according to [1] or [2], whereinthe functional group capable of reacting with an epoxy group is acarboxyl group.

[4] The gas separation membrane module according to any one of [1] to[3], wherein the hardener is an acid anhydride.

[5] The gas separation membrane module according to any one of [2] to[4], wherein the curing accelerator is an imidazole compound.

Section C: a separation membrane module and so on satisfactorilyoperable even at high temperature

Technical Field

The invention disclosed in this section relates to a gas separationmembrane module having a hollow fiber element wherein a hollow fiberbundle including a number of hollow fiber membranes with selectivepermeability is fixed by tube sheet prepared by curing a particularepoxy resin composition. In particular, the invention relates to aseparation membrane module satisfactorily operable at high temperatureby reducing influence of thermal expansion of a tube sheet.

Background Art

The hollow fiber type gas separation membrane module generally has ahollow fiber element including a fiber bundle comprising a number ofhollow fiber membranes with selective permeability, and a hollow vesselhousing the element. Both ends or one end of the hollow fiber bundle inthe hollow fiber element are fixed to the end of the vessel by theresin-cured plate (tube sheet). The vessel has, at least, a feed gasinlet, a permeate gas outlet and a non-permeate gas outlet.

In a gas separation membrane, generally, the higher temperature andpressure of feed gas are, the larger gas permeation rate is. Thereforewhen a gas separation module is used, it is sometimes considered tocompress the feed gas before being fed to the module for example by acompressor. The compressed gas may be fed at very high temperature of149° C. to 260° C.

When the separation membrane module is used under high-temperatureconditions as described above, thermal expansion of a tube sheet maycause, for example, stress concentration within the tube sheet, orcracks in the tube sheet due to the stress concentration which may causeloss of airtightness in the separation membrane module. Especially,high-temperature gas compressed by a compressor or the like is generallycooled before being fed to the gas separation membrane module. There isroom for improvement in conventional separation membrane modules interms of the use at high temperature (e.g. designing components moreeffectively by taking the special condition of high temperature intoconsideration). Furthermore, whether separation membrane module is for ahigh temperature or not, it is required to simplify a structure of theseparation membrane module and to develop structures which cancontribute to downsizing.

In the light of the above problems, an objective of the invention inthis section is to provide a separation membrane module which cansatisfactorily operate at high temperature, with the influence ofthermal expansion of the tube sheet being minimized. Another objectiveis to provide a structure advantageous to downsizing and weight savingby simplifying the structure of a separation membrane module.

The summary of the main invention disclosed in this section is asfollows.

[1] A separation membrane module using on high-temperature conditions,comprising;

a hollow fiber bundle including a number of hollow fiber membrane withselective permeability,

a cylindrical vessel housing the hollow fiber bundle,

a tube sheet placed at the end of the hollow fiber bundle, which fixesthe end of the bundle to the end of the cylindrical vessel and separatesthe inside of the cylindrical vessel from the outside, and

an annular sealing member for sealing member for sealing between theouter surface of the tube sheet and the inner surface of the cylindricalvessel;

wherein the tube sheet does not have any step in a portion around theplace to which a sealing member is attached.

According to such a configuration, since there is no steps in the tubesheet on the periphery of the place on which the annular sealing member(detailed below) is mounted, influence of stress concentration in useunder high temperature can be reduced in comparison with conventionalstructures in which the tube sheet has step(s) for O-ring.

The term, “annular sealing member” as used in this section means anannular sealing member which seals between the outer surface of a tubesheet and the inner surface of a cylindrical vessel, and there are noparticular restrictions to its cross-sectional shape. The annularsealing member can be, for example, an O-ring (substantially circularcross section), or can be V- or U-packing having a substantially V- orU-shaped cross section, respectively. Furthermore, its cross section canbe elliptic, rectangular, polygonal or X-shaped.

The term, “under the high-temperature conditions” means a temperature inthe range of 80° C. to 300° C.

The term, “cylindrical vessel” includes not only those with both endsbeing open but also those with one end being open.

A gas separation membrane module can be used for applications such asseparation of oxygen, nitrogen, hydrogen, water vapor, carbon oxide oran organic vapor.

First Embodiment in Section C

FIG. 5 schematically shows a basic configuration of a gas separationmembrane module. In the following description, there will be describedseveral embodiments, which are not independent of each other and thecontents of these embodiments can be combined as appropriate.

A gas separation membrane module 1, as shown in FIG. 5, has a hollowfiber bundle 15 of hollow fiber membranes 14 with selective permeabilityand a substantially cylindrical vessel 10 housing the hollow fiberbundle 15. The cylindrical vessel 10 is made of for example metal andhas openings at both ends. The cylindrical vessel 10 can have acircular, elliptic or polygonal cross section. The case having acircular cross section (that is, the vessel 10 is cylindrical) will bedescribed below.

The hollow fiber membrane 14 can be used conventional well-knownmembrane and can be made of any materials as long as it has gasseparation ability. For example, it is suitably made of polymermaterial, which is glassy at normal temperature (23° C.) such as, inparticular, polyimide, polysulfone, polyetherimide, polyphenylene oxideand polycarbonate for their gas separation ability.

The hollow fiber bundle 15 can be of about 100 to 1,000,000 hollow fibermembranes. There are no particular restrictions to the shape of thecollected hollow fiber bundle, however a cylindrical hollow fiber bundleis preferable in the light of easiness in production and pressureresistance of a vessel. FIG. 5 shows an embodiment in which hollow fibermembranes are disposed substantially in parallel, however, these hollowfiber membranes can be cross-arranged.

Again referring to FIG. 5, tube sheets 30 are placed at the end of thehollow fiber bundle 15 in each end of the vessel 10, and an annularsealing member 17 is disposed on the periphery of each tube sheet. Theannular sealing member 17 can be, for example, an O-ring (substantiallycircular cross section), or can be V- or U-packing having asubstantially V- or U-shaped cross section, respectively. A case of anO-ring will be described below.

The tube sheet 30 is made of a cured material of epoxy resin composition(detailed below) in this example, and it is formed substantially as adisc-shape to be fitted into the end of the vessel 10. The hollow fibermembranes 14 penetrate this tube sheet 30 in its thickness direction,with the end of each hollow fiber membrane 14 opened to the outersurface of the tube sheet 30. The tube sheet has a function of fixingmany hollow fiber membranes together. The tube sheet also has a functionof maintaining airtightness by separating the internal space of themembranes from the external spaces, and sealing between the hollow fibermembranes as well as between the hollow fiber membranes and the innersurface of the vessel in cooperation with the annular sealing member.

There are no particular restrictions to a cured resin for the tube sheet30 as long as it is resistant to a high temperature and can maintainairtightness of the inside of the hollow fiber module. The resin ispreferably also resistant to water vapor when being used for dehydratingan organic vapor or moisturizing. In general, a thermosetting resin suchas polyurethane or an epoxy resin is suitably used. In the light ofresistance to a high temperature and strength, an epoxy resin isparticularly suitably used. For a nitrogen membrane module, the epoxyresin for example described in Japanese published examined applicationNo. 1990-36287 can be used, whereas for an organic-vapor separationmodule the epoxy resin for example described in WO 2009/044711 can beused. The epoxy resin as disclosed in section B can also be used for thetube sheet in the module of this section.

Caps 20 and 21 are attached to the ends of the cylindrical vessel 10 inthe separation membrane module 1 as shown in FIG. 5. A mixed gas inlet22A is formed in the cap 20, while a non-permeate gas outlet 22B isformed in the cap 21. An outlet 12 for a permeate gas is formed in apart of the peripheral wall of the vessel 10. It is noted that theinvention in this section is mainly characterized in surroundingstructures of the tube sheet 30 as described later, however there are noparticular restrictions to the type of a separation membrane module aslong as it can form such a structure.

A structure in the vicinity of the tube sheet will be described withreference to FIG. 6. FIG. 6(a) shows an exemplary structure of a moduleend according to the invention of this section, while FIG. 6(b) showsanother structure.

An O-ring 18 is mounted between the inner surface of the cylindricalvessel 10 and the outer surface of the tube sheet 530 to ensureairtightness between these members in the gas separation membrane moduleshown in FIG. 6(b). Specifically, there is formed a step 530 s to whichthe O-ring 18 is fitted in a part of the outer circumference of the tubesheet 530. When the gas separation membrane module 101 is used underhigh temperature, stress concentration can occurs in the vicinity of thestep 530 s in the tube sheet 530, depending on the conditions, which maycause troubles such as breakage of the of the tube sheet accompanyingloss of airtightness.

To deal with this problem, according to the structure of thisembodiment, the tube sheet 30 without a step in the outer surface isused as shown in FIG. 6(a). In this example, a diameter of the tubesheet 30 is constant over its full length (for another aspect, describedlater with reference to FIG. 7). A step 10 s is formed at the end of thecylindrical vessel 10, so that a groove for the O-ring 18 can be formedwithin the step. A cross-sectional shape of the groove is, for example,a rectangle. The O-ring 18 is to be fitted into the groove, to ensureairtightness between the outer surface of the tube sheet and the innersurface of the cylindrical vessel.

The O-ring 18 is also firmly contacted to the inner surface of the cap20, so that airtightness can be also ensured between the vessel end andthe cap inner surface. According to such a configuration, the one O-ring18 contributes to sealing both (i) between the tube sheet and thecylindrical vessel and (ii) between the cap and the cylindrical vessel,thus the necessity of additional O-ring(s) can be eliminated.

There are no particular restrictions to means for fixing the cap 20 tothe cylindrical vessel 10, however, various well-known means, forexample such as fixing by an adhesive or by fixture can be employed.

According to the gas separation membrane module in this embodimentconfigured as described above, no step is formed on the tube sheet 30 inthe periphery where the O-ring 18 is to be mounted. Therefore, it isless influenced by stress concentration in use under high temperaturethan conventional structure as shown in FIG. 6(b). As a result,resistance to high temperature and reliability of the gas separationmembrane module 1 as a whole can be improved.

Such advantages can be achieved likewise, in addition to the structureshown in FIG. 6(a), in the structure shown in FIG. 7. That is, means forpreventing transfer of the tube sheet 30 along the axial direction isnot described in the configuration of FIG. 6(a) to simplify theexplanation, however, the configuration of FIG. 7 contains such means.

A step 10 t is formed at a predetermined distance inside from the end ofthe vessel 10 as shown in FIG. 7 in this gas separation membrane module1′. In response to this, there is also formed a step 30 t at the end ofthe tube sheet 30′. The other structural elements are as described inFIG. 6(a). According to such a configuration, the end of the tube sheet30 (right side in this figure) abuts on the step 10 t, to therebyprevent the tube sheet from moving inward along the axial direction.

Although the gas separation membrane module in FIG. 5 has been describedwith reference to an example, the invention in this section is, ofcourse, applicable to another configuration. For example, the inventioncan be suitably applied to a shell feed type module and a purge typemodule where the cylindrical vessel has a purge gas inlet.

Second Embodiment in Section C

FIG. 8 shows an exemplary structure of the module end in the secondembodiment; FIGS. 8(a) and 8(b) show the state at normal temperature andthe state in operation, that is, at high temperature, respectively.

The gas separation membrane module in FIG. 8 has, like the aboveembodiment, a hollow fiber bundle 15 as a collection of a number ofhollow fiber membranes with selective permeability and a cylindricalvessel 10 housing the hollow fiber bundle. Furthermore, it has tubesheets 38 at the ends of the hollow fiber bundle 15 and caps 20 at theends of the cylindrical vessel 10. For structural members similar tothose in the above embodiment, the same symbols as used in the figuresas described above are used without being redundantly described.

As shown in FIG. 8(a), this gas separation membrane module is designedsuch that the diameter of the tube sheet 38 is slightly smaller atnormal temperature than the inner diameter of the inner surface 10 a ofthe cylindrical vessel 10, thus there is a gap between the outer surfaceof the tube sheet 38 and the inner surface 10 a of the cylindricalvessel. The tube sheet 38 is made of, like the above embodiment, a resinmaterial such as an epoxy resin, which has a larger thermal expansioncoefficient than a material for the cylindrical vessel 10 (for example ametal).

This gas separation membrane module is intended to be used, for example,at a temperature in the range of 80° C. to 300° C. As shown in FIG.8(b), when using this module, the tube sheet 38 is warmed to apredetermined temperature, as a result, the diameter of the tube sheetwill be expanded due to thermal expansion, so that its outer surface canbe firmly contacted to the inner surface 10 a of the cylindrical vessel.Such a contact ensures airtightness between these members.

When using the gas separation membrane module, the module is adequatelywarmed to ensure airtightness between the tube sheet 38 and thecylindrical vessel 10 and then a mixed gas is fed.

According t to the above configuration, the tube sheet 38 thermallyexpands to exert the effect of sealing between the tube sheet and thecylindrical vessel. Thus, it can eliminate the necessity for placingother O-ring(s) for sealing between these members or adhering the outersurface of the tube sheet to the inner surface of the cylindricalvessel. Furthermore, when the tube sheet 38 thermally expands, thestress to the cylindrical vessel 10 can be reduced, so troubles such asbreakage of the cylindrical vessel 10 can be advantageously prevented.

Although the above description assumes that the tube sheet and thecylindrical vessel are made of epoxy resin and metal, respectively, thematerial for the cylindrical vessel is not limited to metal as long asthe material has a thermal expansion coefficient smaller than the tubesheet. Although being not shown in FIG. 8, sealing means for sealingbetween the cap 20 and the cylindrical vessel 10 can be used. Forexample, annular sealing member(s) to be disposed between the innersurface of the cap 20 and the outer surface of the cylindrical vessel 10or between the inner surface of the cap 20 and the end face of thecylindrical vessel 10 can be used.

Third Embodiment in Section C

FIG. 9 shows an exemplary module end structure of a module according tothird embodiment. It is noted that although the module in the first andthe second embodiments are intended to be used at high temperature,there are no particular restrictions to an operating temperature for thegas separation membrane module in FIG. 9.

The gas separation membrane module in FIG. 9 has, like the above twoembodiments, a hollow fiber bundle 15 as a collection of a number ofhollow fiber membranes with selective permeability, a cylindrical vessel10 housing the hollow fiber bundle, tube sheet 30 at the end of thehollow fiber bundle 15 and a cap 20 at the end of the cylindrical vessel10. Furthermore, it has an O-ring 18 for sealing between the tube sheetand the cylindrical vessel. For structural members similar to those inthe above embodiments, the same symbols as used in the figures asdescribed above are used without being redundantly described.

In the configuration in FIG. 9, an opening 10 h is formed in a part ofthe peripheral wall of the cylindrical vessel 10, for dischargingpermeate gas passing through the hollow fiber membrane to the outside ofthe cylindrical vessel. Likewise, in a part of the peripheral wall ofthe cap 20, an opening 20 h is formed at the corresponding place. Ahollow discharge pipe 41 is mounted such that it passes through bothopenings 10 h and 20 h. In the gas separation membrane module in FIG. 9,the permeate gas outlet 12 as in FIG. 5 is not formed, since thedischarge pipe 41 can serve as the permeate gas outlet 12.

This discharge pipe 41 also can act as means for fixing the cap 20 tothe cylindrical vessel 10. That is, the discharge pipe 41 passes throughboth openings 10 h and 20 h, so that transfers in both the axial and therotational directions between the cap 20 and the cylindrical vessel 10are restricted.

To connect these members 10 and 20 more firmly, additional fixingscrew(s) 42 can be used as shown FIG. 9. The fixing screw 42 is screwedinto a threaded hole formed in the peripheral wall of the cap 20, andits tip in inserted into a part of the peripheral wall of thecylindrical vessel 10. A female screw part, into which the screw 42 isto be engaged, can be formed in the cap 20 or the cylindrical vessel. Afixing pin can be used instead of the fixing screw.

It is noted that there can be an annular sealing member (not shown) forsealing between the inner surface of the peripheral wall of the cap 20and the outer surface of the cylindrical vessel 10. It can ensure morereliable airtightness between the cap 20 and the cylindrical vessel 10.However, such member can be omitted, if the O-ring 18 can satisfactorilyseal both between the tube sheet and the cylindrical vessel and betweenthe cap and the cylindrical vessel.

In the configuration described above, the member 41 for forming thechannel for discharging permeate gas also acts as means for fixing thecap 20 and the cylindrical vessel 10. Thus, the module structure can besimplified, resulting in weight- and size-reduction of the module.

The example shown in FIG. 9 has been described with reference to thedischarge pipe 41 for discharging permeate gas passing through thehollow fiber membrane to the outside of the cylindrical vessel. However,another tubular member forming a channel communicating the inside withthe outside of the cylindrical vessel can be used, instead of thedischarge pipe 41.

Alternatively, the cap 20 can be fixed to the cylindrical vessel 10 onlyby fixing member such as the fixing screw 42 or fixing pin, withoutusing the discharge pipe 41 passing through the openings 10 h and 20 hin the vessel and the cap. Such a configuration is advantageous for sizereduction of a module, compared with the configuration of FIG. 10(b)where flanges are fixed to each other as described later, since theflanges can be omitted in the present configuration.

One or two or more fixing members can be used, and when two or moremembers are used, the fixing members are preferably evenly disposed in acircumferential direction.

Other Embodiments in Section C

The invention in this section can be, besides the embodiments describedabove, as shown in FIGS. 10(a) and (b). Each gas separation membranemodule has, like the above embodiments, a hollow fiber bundle 15 as acollection of a number of hollow fiber membranes, a cylindrical vessel10 housing the bundle, a tube sheet 30 at the end of the hollow fiberbundle 15 and caps (26, 27) at the end of the cylindrical vessel.Furthermore, it has the O-ring 18 for sealing between the outer surfaceof the tube sheet and the inner surface of the cylindrical vessel.

In the configuration in FIG. 10(a), the cap 26 is to be fixed to thecylindrical vessel 10 by a screw system. Specifically, in theconfiguration, a female screw formed in a part of the inner surface ofthe cap 26 is to engage with a male screw formed in a part of the outersurface of the cylindrical vessel 10. In the state where the cap 26 isrotated to a predetermined position (see FIG. 10(a), the O-ring 18partially abuts on the inner surface of the cap 26, ensuringairtightness between the cylindrical vessel end and the cap innersurface. Like the above embodiments, the O-ring 18 also ensuresairtightness between the outer surface of the tube sheet and the innersurface of the cylindrical vessel.

In the configuration of FIG. 10(b), a flange 27 f is formed in the cap27, while a corresponding flange 10 f is formed in the cylindricalvessel 10. By connecting the flanges 27 f and 10 f with fixtures 43, thecap 27 can be fixed to the cylindrical vessel 10. The fixture 43 can be,for example, a bolt-nut system. Alternatively, threaded hole formed inthe flange 10 f and bolt can be used. There are no particularrestrictions to positions where flanges are tightened up by the fixtures43, but the tightening positions are preferably located at regularintervals in a circumferential direction of the flange.

Further Embodiment in Section C

A gas separation membrane module of the invention in this section canhave a configuration as shown in FIG. 11. FIG. 11(a) is across-sectional view showing an exemplary gas separation membranemodule, and FIG. 11(b) is an enlarged partial view of FIG. 11(a).

The gas separation membrane module in FIG. 11 has a hollow fiber bundle115 as a collection of hollow fiber membranes, a cylindrical vessel 110housing the bundle, tube sheets 130A, 130A at both ends of the hollowfiber bundle 115 and caps 120, 121 at the end of the cylindrical vessel110. Furthermore, the module has the module has the O-ring 118 arrangedon the outer surface of each tube sheet 130A.

The cylindrical vessel 110 of this example has a tubular member 111extending along the longitudinal direction of the module, and endmembers 112, 112 attached at the each end of the member 111. In theperipheral wall of the end member 112 in the left side of the figure(gas inlet side), an outlet 112 h for a permeate gas (as an example) isformed.

Each end member 112 has a flange 112 f. Meanwhile, the caps 120, 121have flanges 120 f, 121 f, respectively. By engaging the flange 112 f ofthe end member with the flange 120 f of the cap, using for examplebolt-nut system (not shown in FIG. 11) as illustrated in FIG. 10, thecap 120 can be fixed to the end member 112 (a similar configuration canbe applicable to the cap 121).

As shown in FIG. 11(b), in this example, the tube sheet 130A is arrangedsuch that it is firmly contacted to both a part of the inner surface ofthe cap 120 and a part of the inner surface of the cylindrical vessel110. Each tube sheet 130A has an outer surface formed as a step like thetube sheet 30′ in FIG. 7, the step in the outer surface of the tubesheet abuts on the step in the inner surface of the cylindrical vessel,thereby the position of the tube sheet 130A in an axial direction(lateral direction in the figure) is secured.

Inside in the radial direction of the flange 120 f of the cap 120, thereis formed an annular step 120 s. An O-ring 118 is disposed within anannular groove, which has a rectangular cross section formed by the step120 s and a part of the flange 112 f in the end member 112. The O-ring118 contributes to ensure airtightness not only between the tube sheet130A and the cap 120 but also between the cap 120 and the end member112.

Although a surrounding structure of the O-ring 118 has been describedwith reference to the structure of the cap 120, the cap 121 side has asimilar structure. Means for fixing a flange is not limited to abolt-nut system, but can be for example configuration where a bolt tipis screwed into a threaded hole formed in either the flange 112 f or 120f.

According to the configuration as described for FIG. 11, like the firstembodiment, any step is not formed in the vicinity of the position ofthe tube sheet 130A where the O-ring 118 is to be mounted. Thus, it canbe less influenced by stress concentration when being used at hightemperature than conventional structure as shown in FIG. 6(b). As aresult, resistance to the high temperature and reliability can beimproved in the gas separation membrane module as a whole.

Furthermore, in the configuration in the configuration FIG. 11, thecylindrical vessel 110 includes a tubular member 111 and the end members112, 112, and such a configuration is advantageous in that material foreach member can be appropriately selected depending on the requirementof the members. It is noted that the invention in this section is notlimited to it, but a single cylindrical vessel can be employed, in whichfor example the tubular member 111 and the end member 112 are integrallycombined.

Furthermore, other gas separation membrane module of the invention inthis section can be as shown in FIG. 12. In this module, principallylike the configuration in FIG. 10(b), the cap 127 is connected to thecylindrical vessel 110′ in such a manner that the flange 127 f in thecap 127 abuts on the flange 110 f in the cylindrical vessel 110′. Thenumber and the disposition of O-rings are different from that in FIG.10(b). The tube sheet 130B is firmly contacted, like that in FIG. 11, tothe parts of the inner surfaces of the cap 127 and the cylindricalvessel 110′.

A first O-ring 118 is disposed within an annular groove 127 g formed inthe inner surface of the cap 127, ensuring airtightness between the tubesheet 130B and the cap 127. The annular groove 127 g is formed, but notlimited to, limited to, slightly inside (left side in the figure) fromthe end face in the side of the flange 127 f in the inner surface of thecap 127.

A second O-ring 119 is disposed between the flange 110 f and the flange127 f. In this example, the O-ring 119 is disposed in the annular groove110 g formed in the flange 110 f in the cylindrical vessel 110. TheO-ring 119 is not an essential element, but it can prevent the gas fromleaking through the space between the flanges 110 f and 127 f.

Of course, such a configuration of the O-rings 118, 119 is not limitedto the embodiment illustrated in FIG. 12, but it can be used incombination with the above embodiments as appropriate. Furthermore, thegroove in which the second O-ring 119 is disposed can be formed in theflange 127 f in the cap 127.

The invention related to section C is as follows.

[1] A separation membrane module used under high-temperature conditions,comprising;

a hollow fiber bundle including a number of hollow fiber membrane withselective permeability,

a cylindrical vessel housing the hollow fiber bundle,

a tube sheet placed at the end of the hollow fiber bundle, which fixesthe end of the bundle to the end of the cylindrical vessel and separatesthe inside of the cylindrical vessel vesselrom the outside, and

an annular sealing member for sealing between the outer surface of thetube sheet and the inner surface of the cylindrical vessel;

wherein there is not a step in the tube sheet on the periphery of theplace on which the annular sealing member is to be mounted.

[2] A separation membrane module used under high-temperature conditions,comprising;

a hollow fiber bundle including a number of hollow fiber membrane withselective permeability,

a cylindrical vessel housing the hollow fiber bundle, and

a tube sheet placed at the end of the hollow fiber bundle, which fixesthe end of the bundle to the end of the cylindrical vessel and separatesthe inside of the cylindrical vessel from the outside;

wherein the tube sheet is made of material having a larger thermalexpansion coefficient than that of material for the cylindrical vessel,and

There is a gap between the outer surface of the tube sheet and the innersurface of the cylindrical vessel at normal temperature, whereas thetube sheet can expand by heating to a predetermined temperature, so thatits outer surface adheres tightly to the inner surface of thecylindrical vessel to provide sealing effect.

[3] A gas separation membrane module, comprising;

a hollow fiber bundle including a number of hollow fiber membrane withselective permeability,

a cylindrical vessel housing the hollow fiber bundle,

a tube sheet placed at the end of the hollow fiber bundle, which fixesthe end of the bundle to the end of the cylindrical vessel and separatesthe inside of the cylindrical vessel from the outside, and

a cap at the end of the cylindrical vessel;

wherein a tubular member for forming a channel communicating the insidewith the outside of the cylindrical vessel penetrates a part of thecylindrical vessel and a part of the cap along the radial direction.

[4] The gas separation membrane module as described in [3], comprising afixing member which is to be inserted into a part of the peripheral wallof the cap and which acts as means for fixing the cap and thecylindrical vessel.

[5] A gas separation membrane module, comprising;

a hollow fiber bundle including a number of hollow fiber membrane withselective permeability,

a cylindrical vessel housing the hollow fiber bundle,

a tube sheet placed at the end of the hollow fiber bundle, which fixesthe end of the bundle to the end of the cylindrical vessel and separatesthe inside of the cylindrical vessel from the outside, and

a cap at the end of the cylindrical vessel;

further comprising a fixing member, which is to be inserted into a partof the peripheral wall of the cap, for fixing the cap to the cylindricalvessel.

[6] A gas separation membrane module, comprising;

a hollow fiber bundle including a number of hollow fiber membrane withselective permeability,

a cylindrical vessel housing the hollow fiber bundle,

a tube sheet placed at the end of the hollow fiber bundle, which fixesthe end of the bundle to the end of the cylindrical vessel and separatesthe inside of the cylindrical vessel from the outside,

a cap at the end of the cylindrical vessel, and

an annular sealing member for sealing member for sealing between theouter surface of the tube sheet and the inner surface of the cylindricalvessel;

wherein the cap is fixed to the cylindrical vessel, by a system

(i) using a thread formed in a part of the inner surface of the cap anda thread formed in an opposite part of the outer surface of thecylindrical vessel, or

(ii) binding a flange of the cap to a corresponding flange of thecylindrical vessel using a fixture.

[7] The gas separation membrane module as described in any of [3] to[6], wherein the annular sealing member further seals between the capand the cylindrical vessel.

Section D: gas separation membrane module whereby which can be reduce areplacement cost and is advantageous in simplifying its structure

Technical Field

The invention disclosed in this section relates to a gas separationmembrane module for gas separation using a number of hollow fibermembranes with selective permeability. In particular, the inventionrelates to a separation membrane module which can reduce replacementcost and is advantageous for simplifying its structure.

Background Art

A hollow fiber type gas separation membrane module generally has ahollow fiber element having a fiber bundle including a number of hollowfiber membranes with selective permeability, and a cylindrical vesselhousing the element. One or both ends of the hollow fiber bundle in thehollow fiber element is attached to the end of a vessel by a resin curedplate (tube sheet). Capping members are attached to the ends of thecylindrical vessel to seal the inside of the vessel.

In conventional gas separation membrane module, as described above, thecylindrical vessel and capping members attached to the cylindricalvessel as a whole constitute a single case. Thus, when the separationmembrane module is replaced, the whole module must be change. Therefore,capping members that are no need to be changed are obliged to bereplaced, leading to higher cost for a replacement part.

On the other hand, it would be possible to make the hollow fiber elementin the case replaceable, but in such a configuration for example, it isnecessary to provide some structure allowing for removal of the hollowfiber element, with inside of the case, therefore module structurebecome more complex and may be disadvantageous to weight reduction.

In view of the problems, an objective of the invention in this sectionis to provide a gas separation membrane module which can reduce areplacement cost, advantageous to simplifying a structure and allow foreasy size- and weight-reduction.

The summary of the main invention disclosed in this section is asfollows.

[1] A gas separation membrane module, comprising;

a cartridge housing a hollow fiber bundle including a number of hollowfiber membranes in a cylindrical vessel,

capping members each of which is configured to be attached to an end ofsaid cartridge,

a sealing member for sealing between each of said capping members andsaid cartridge, and

a fixture for fixing said capping members to each other,

wherein said cartridge is replaceably mounted between said cappingmembers.

According to such a configuration, there is provided a gas separationmembrane module which can reduce a replacement cost, is advantageous tosimplifying a structure and can be easily size- and weight-reduced.

Embodiment in Section D

There will be described one embodiment of the invention in this sectionwith reference to the drawings. The invention in this section is notlimited to the following embodiment, but can be, if necessary, modified,including addition or omission of a component and change of a shape.

As shown in FIG. 13, a gas separation membrane module 201 (hereinafter,sometimes simply referred to as “separation membrane module”) has acylindrical cartridge 210 housing a hollow fiber bundle 215, cappingmembers 220, 221 at both ends of the cartridge and, for example, afixing rod 245 for connecting these capping members 220, 221 to eachother.

The cartridge 210 includes a cylindrical vessel 211 with open ends, thehollow fiber bundle 215, and tube sheets 230, 231. The tube sheets 230,231 hold the ends of the hollow fiber bundle 215 and separate the insideand the outside of the cylindrical vessel 211.

The hollow fiber bundle 215 can be made of known structure. The hollowfiber bundle 215 can be, for example, a collection of about 100 to1,000,000 hollow fiber membranes 214. There are no particularrestrictions to a material for the hollow fiber membrane 214 as long asthe membrane can separate gases. For example, it is suitably made ofpolymer material, which is glassy at normal temperature (23° C.) suchas, in particular, polyimide, polysulfone, polyetherimide, polyphenyleneoxide and polycarbonate which exhibits higher gas separation ability.There are no particular restrictions to a shape of the collected hollowfiber bundle, but in the light of easiness of production and pressureresistance of a vessel, it can be hollow fiber bundle as a cylindricalcollection. FIG. 13 shows an embodiment in which hollow fiber membranes214 are disposed substantially in parallel, however, these hollow fibermembranes can be cross-arranged.

The cylindrical vessel 211 can have any shape of cross section such ascircular, elliptic or polygonal. There will be described a circularshape. The cylindrical vessel 211 can be formed for example byprocessing a single metal pipe. In this embodiment, it is preferablethat, for example, fixing mechanism for fixing the capping members 220,221 to the cylindrical vessel 211 is not arranged in the cylindricalvessel 211 as a cartridge (in other words, a structure where cappingmembers are not to be connected to the cylindrical vessel may bepreferable). The configuration can eliminate the necessity forprocessing the cylindrical vessel 211 such as forming a flange, forminga threaded hole and placing a fixing pin.

An inner groove 217 is formed near the end in the inside of thecylindrical vessel 211, as shown in FIG. 14, where the inner diameter ispartially longer. A part of tube sheet 230, 231 is configured to befitted into the inner groove 217 as described later. Another innergroove 218 is formed further inside from the inner groove 217 by apredetermined distance (in a direction away from the end). With respectto the inner grooves 217 and 218, cross-sectional shape of the groovesmay be any shape such as rectangular, substantially rectangular,substantially rectangular, trapezoidal or substantially trapezoidal.

Openings 212 for discharging gas from the vessel are formed in the partwhere the inner groove 218 is formed. The number and the positions ofthe openings 212 are not particularly limited. For example, the openings212 can be formed on the periphery of the cylindrical vessel 211 atregular intervals. As shown in FIG. 14, an outer annular groove 219 forelastic ring member R2 described later is formed on the periphery of thetubular member 211 and positioned slightly inwardly from the innergroove 218 (in a direction away from the cylinder end).

Sealing members 230 and 231 (see FIG. 13) in the cartridge 210 are forexample made of an epoxy resin and formed as a substantially disc-shapeto be fit into the end of the vessel 211. Since the tube sheets 230 and231 have a similar structure in principle, there will be described onlythe tube sheet 230. Each hollow fiber membrane 214 penetrates the tubesheet 230 along its thickness direction, and the end of each hollowfiber membrane 214 is open at to the outside of the tube sheet 230. Thetube sheet 230 adheres the hollow fiber membranes 214 together, andseparates the inside of the cylindrical vessel 211 from the outside.There are no particular restrictions to a cured resin forming the tubesheet as long as it is adequately durable and can ensure airtightness ofthe inside of the hollow fiber module. The resin is also preferablyresistant to water vapor when being used for dehydrating ormoisturizing. In general, a thermosetting resin such as polyurethane andan epoxy resin is suitably used. In the light of durability andstrength, an epoxy resin is particularly suitably used. For a nitrogenmembrane module, the epoxy resin for example described in Japanesepublished examined application No. 1990-36287 can be used, whereas foran organic-vapor separation module the epoxy resin for example describedin WO 2009/044711 can be used. The epoxy resin as disclosed in section Bcan also be used for the tube sheet in the module of this section. Thetube sheet can be formed by known method such as centrifugal molding orstationary molding.

It is noted that the term “separate” (e.g. separating the inside of acylindrical vessel from the outside by a tube sheet) as used above meansthat substantial isolation by the tube sheet is acceptable and the outercircumference of the tube sheet does not necessarily have to adhere tothe inner surface of the cylindrical vessel.

As shown in FIG. 13, the part of the tube sheet 230 extrudes from theend of the cylindrical vessel 211, and a chamfer (tapered surface) isformed along the periphery of the end of the tube sheet 230. The tubesheet 230 can be formed by for example the following process. First, forexample a mold (not-shown) is attached to the end of the cylindricalvessel 211, with the hollow fiber bundle 215 being disposed within thecylindrical vessel 211. Then, a resin is injected into the mold and thecylindrical vessel 211, and then cured. After the resin is cured, themold is detached and the end of the cured resin is cut to form the endface of the tube sheet 230 and to make the ends of the hollow fibermembranes 214 opened. The chamfer in the tube sheet 230 can be formed bymolding or by secondary processing after resin curing.

Since the cylindrical vessel 211 has the inner groove 217, the groove217 is filled with the resin for the tube sheet 230. Consequently, thepart of the tube sheet 230 can engage with the inner groove 217, so thatthe tube sheet 230 can be positioned relative to the cylindrical vessel211 in an axial direction. Generally, during operation of the separationmembrane module 201, the pressure is applied to the tube sheet 230 insuch a direction that the member is pushed into the cylindrical vessel211. According to the configuration of this embodiment, the part of tubesheet 230 engages with the inner groove 217. Therefore, the tube sheet230 can be prevented from moving into the cylindrical vessel 211 bypressure during operation.

Next, there will be described a structure of the capping members 220,221 with reference to FIGS. 13 and 15. Since the capping members 220,221 basically have a similar structure in this example only the cappingmember 220 will be described, and for the capping member 221 onlydifferent parts will be described. There are no particular restrictionsto materials for the capping members 220 and 221, however they can befor example made of metal. It is noted that the capping members 220, 221can have different shape from each other, and the shapes of the cappingmembers 220, 221 can be appropriately changed depending on theapplication and specifications of the separation membrane module.

As shown in FIGS. 13 and 15, the capping member 220 has a bottomedcylindrical shape. Specifically, as shown in FIG. 15(A), it has an endface 220A covering the opening of the cylindrical vessel 211 and acylindrical part 220B extending from the edge of the end face.

The end face 220A has a gas inlet P1 for introducing mixed gas. Innergrooves 227 a, 227 b are formed on the inside of the cylindrical part220B. An elastic ring member R1 (detailed below) is to be fitted intothe inner groove 227 a as shown in FIG. 13. The other inner groove 227 bis for forming a gas channel P3 surrounding the cylindrical vessel 211when the capping member 220 is attached to the cylindrical vessel 211.The other capping member 221 has a non-permeate gas outlet P2.

The gas channel P3 (FIG. 13) communicates with the openings 212 of thecylindrical vessel 211, such that the gas in the vessel flows into thegas channel P3 through each opening 212. The gas is discharged to theoutside via the outlet 223 formed in the cylindrical part 220B in thecap. An element (opening) corresponding to the outlet 223 is not formedin the capping member 221 in the configuration in FIG. 13, however,depending on, for example, an application of the module, the opening canbe formed in the capping member 221, while in response to that, openings212 can be formed in the cylindrical vessel 211.

Again referring to FIG. 15, the cylindrical part 220B has through-holes220 h through which fixing rod 245 (FIG. 13, detailed below) is insertedrespectively. Six through-holes 220 h are disposed at regular intervalsin a circumferential direction in this example. According to theconfiguration such as the cylindrical part 220B has through-holes 220 hthrough which the fixing rod 245 is inserted, the following advantagescan be obtained. That is, in this configuration, since the cylindricalpart 220B as the part of the cap 220 holds the fixing rod 245, there isno need to provide any special structure for holding the fixing rod withthe capping member 220. Therefore, the capping member 220 and thus theseparation membrane module 201 can be size-reduced, contributingweight-reduction in the module.

It is noted that the number of the fixing rods 245 is not limited to 6,but can be 1 to 5 or 7 or more. For example, as shown in FIG. 16, it canbe 3, 4 or 8. The fixing rod 245 can be, for example, made of, but notlimited to, a metal.

As shown in FIG. 15(B), a flat part 220 f is formed on the part of thecylindrical part 220B where the outlet 223 opens, by cutting the part ofthe cylindrical part 220B. Furthermore, in the bottom of the cylindricalpart 220B1, for example, a flat part 220 g for preventing the separationmembrane module from rolling is formed.

An elastic sealing member R1 for sealing between the tube sheet 230 andthe capping member 220 is fitted in the inner groove 227 a of thecapping member as shown n FIG. 13. The elastic ring member R1 isconfigured such that it remains on the inside of the capping member 220when the cartridge 210 is detached from the capping member 220 forreplacement. The elastic ring member R1 can be, for example, an O-ring(substantially circular cross section). Alternatively, it can be a V- orU-packing with a substantially V- or U-shaped cross section,respectively. Furthermore, its cross section can be elliptic,rectangular, polygonal or X-shaped.

Another elastic ring member R2 is disposed between the cylindricalvessel 211 and the cylindrical part 220B, such that it is fitted intothe periphery groove 219 of the cylindrical vessel 211, to seal betweenthese members. The elastic ring member R2 can be also selected from avarious types such as an O-ring, a V-packing and a U-packing asdescribed above.

As shown in FIGS. 13 and 15, the capping members 220, 221 are connectedto each other with six (for example) fixing rods 245 and nuts 246mounted on both ends. In this embodiment, it is the fixtures as separatecomponents from the cartridge 210 that connect the capping members 220,221. Therefore, there is no need to provide any structure such asflanges with the cartridge 210 (particularly, the tubular member 211),resulting in simplifying the structure of the cartridge 210.

There are no particular restrictions to a fixture for fixing the cappingmembers 220, 221, but it can be selected from various types. Forexample, one end of the fixing rod can be a head with a larger diameter,while the other end can receive a nut. Alternatively, the innercircumference of the through-hole 220 h of the inner capping member 220can be threaded, while in response to that, the rod end can be alsothreaded, so that the rod end is to be screwed into the through-hole 220h. Alternatively, mechanisms for mechanically binding and fixing cappingmembers can be used; such as a mechanism for fixing the module byclamping both ends of the module (capping members 220, 221).

In addition, such mechanisms are not limited to the ones for connectingcapping members 220, 221 to each other. Instead, mechanism for securingeach capping members 220, 221 to a predetermined fixing position can beused, in which the cartridge 210 is removably mounted between thecapping members 220 and 221. For example, a particular configuration canbe employed, where some part of an apparatus or facility on which theseparation membrane module is to be mounted is configured to serve as abase member (not shown), and each of the capping members 220, 221 can befixed to the base member.

In the separation membrane module 201 of this embodiment, for example,gas separation is conducted as follows. A pressurized air is introducedinto the inside of the vessel through the gas inlet P1, and the air isfed into the inside of the hollow fiber membrane 214 via the open end.While the pressurized air flows in the hollow fiber membrane 214, anoxygen-rich air selectively permeates toward the outside of themembrane, and the permeating oxygen-rich air moves into the space wherethe hollow fiber bundle between tube sheets is mounted. The permeate gasis discharged from openings 212 and 223 as permeate gas outlets. On theother hand, the non-permeating nitrogen-rich air is discharged, throughthe other opening in the hollow fiber membrane 214, from thenon-permeate gas outlet P2 as non-permeate gas outlet.

According to the gas separation membrane module 201 described above, ithas the configuration in which the cartridge 210 housing the hollowfiber bundle 215 is to be mounted between the capping members 220, 221.Thus, the module can be replaced only by changing the cartridge withoutchanging the whole module, therefore cost for the replacement part canbe reduced.

On the other hand, a structure may be adopted in which only the innercomponents corresponding to the hollow fiber element 215, however, it isnecessary to design a structure for mounting/removing the replaceablecomponent within the cylindrical vessel 211 in this case. In contrast,according to the module 201, complex structures are not required, sincethe cylindrical vessel 211 (as a part of the cartridge 210) itself canserve as the case for the module 201. This is advantageous in weightreduction for the whole separation membrane module 201, particularlysuitably applicable to a field needing weight reduction of the modulesuch as aeronautical field.

Furthermore, according to the above configuration, the capping members220, 221 are coupled by fixture (245, 246) as separate component fromthe cartridge 210. It is, therefore, not necessary to providestructure(s) for coupling the capping member with the cylindrical vessel211 (for example, a flange). Thus, a structure of the cartridge 210 canbe simplified and a production cost can be reduced.

According to the above configuration, the elastic ring member R1 is seton the inner circumference of the capping member 220, 221 such that thering member R1 remains in the capping member side when the cartridge 210is removed during replacement. Such a configuration is advantageous tosaving production cost for the cartridge 210 compared with forming thering member R1 in the side of the cartridge 210.

As shown in FIG. 13, in the configuration of this embodiment, thechamfer (tapered surface) is formed along the periphery of the end ofthe tube sheet 230, therefore, the end of the tube sheet 230 can besmoothly inserted into the elastic ring member R1.

The embodiments of this invention in this section have been describedwith reference to the drawings, however, there can be variousmodifications of the invention in this section in addition to thatillustrated in the drawings. For example, the shape and the position ofa sealing member for sealing between members can be appropriatelychanged. In addition to the elastic ring members R1, R2, additionalsealing member can be used.

Although there has been illustrated a configuration in which the elasticring member R2 is fitted into the periphery of the cylindrical vessel211 in the above embodiment as shown in FIG. 13, the invention of thissection is not limited to that, but can be a configuration in which theelastic ring member R2 is disposed in the inner circumference of thecapping member 220, 221 and during replacement of a cartridge, theelastic ring member R2 is to remain in the side of the capping member220, 221. It can eliminate the necessity of forming the periphery groove219 in the cylindrical vessel 211 in the cartridge 210, resulting infurther reducing a production cost for the cartridge 211.

Although the examples of separation membrane modules constituting aso-called bore feed type in the above embodiment, the invention in thissection can be applied to the separation membrane module constituting ashell feed type. In such a case, a configuration can be employed inwhich the cartridge suitable to a shell feed type is replaceably mountedbetween the capping members as described above.

The inventions according to section D are as follows.

[1] A gas separation membrane module, comprising;

a cartridge housing a hollow fiber bundle ding a number of hollow fibermembranes in a cylindrical vessel,

capping members each of which is configured to be attached to both endof said cartridge,

a sealing member for sealing between each of said capping members and dsaid cartridge, and

a fixture for fixing said capping members to each other,

wherein said cartridge is replaceably mounted between said cappingmembers.

[2] The gas separation membrane module as described in [1], wherein

said fixture has at least one fixing rod coupling said capping members,and

each capping member has a through-hole into which said fixing rod isinserted.

[3] The gas separation membrane module as described in [1] or [2],wherein

said capping member is mounted such that it covers the end of saidcylindrical vessel, and

said sealing member is an elastic ring member configured to be disposedbetween the periphery of said cartridge and the inner circumference ofsaid capping member.

[4] The gas separation membrane module as described in [3], wherein saidelastic ring member is to be held in the inner circumference of saidcapping member, and is configured to remain in the side of said cappingmember when said cartridge is removed from said capping member forreplacement.

[5] The gas separation membrane module as described in any of [1] to[4], wherein

said cartridge has a tube sheet holding the end of said hollow fiberbundle, for separating the inside of said cylindrical vessel from theoutside,

an inner groove is formed in a region within said cylindrical vessel andfacing said tube sheet and

a part of said tube sheet engages with said inner groove.

Section E: Gas Separation Membrane Module Capable of More EfficientlySeparating Gases

Technical Field The invention in this section relates to a gasseparation membrane module for separating gases with a hollow fibermembrane, in particular a gas separation membrane module which can moreefficiently separate gases in a so-called bore feed type module.

Background Art

A hollow fiber type gas separation membrane module generally has ahollow fiber element including a hollow fiber bundle comprising a numberof hollow fiber membranes with selective permeability and a hollowcasing housing the element. Both ends or one end of the hollow fiberbundle in the hollow fiber element are fixed by resin-cured plate (tubesheet). Furthermore, the casing has a mixed gas inlet, a permeate gasoutlet and an non-permeate gas outlet.

For the purpose of efficient gas separation, for example, Japanesepublished unexamined application No. 2000-262838 discloses a gasseparation membrane as a so-called bore feed type module in which mixedgas is fed into hollow fiber membranes, wherein a part of the hollowfiber bundle is covered by a film member, so that the carrier gasoutside of the hollow fiber membranes and the mixed gas inside of themembranes flow countercurrently.

According to the above gas separation membrane module in No.2000-262838, the flow direction of the carrier gas can be regulated toachieve more efficient gas separation, however, it is important toimprove an efficiency of gas separation even in the bore feed typemodules without using a carrier gas (purge gas). In view of the aboveproblem, an objective of the invention in this section is to provide abore feed type gas separation membrane module which can more efficientlyseparate gases.

The summary of the main invention disclosed in this section is asfollows.

[1] A gas separation membrane module comprising;

a hollow fiber bundle as a collection of a number of hollow fibermembrane with gas separation ability,

a casing having a mixed gas inlet, a permeate gas outlet and anon-permeate gas outlet, in which said hollow fiber bundle is disposed,and

two tube sheets for fixing both ends of said hollow fiber bundle,

in which mixed gas from said mixed gas inlet is fed into said hollowfiber membrane, while the mixed gas partly permeates the membrane, toachieve gas separation,

wherein,

(i) a structure for feeding purge gas is not provided, said purge gas isfor purging permeate gas from hollow fiber membrane, and

(ii) the module further comprising, a gas-impermeable film memberwrapped around the outer surface of said hollow fiber bundle, in whichone end substantially abuts on said tube sheet in the downstream sidealong the mixed-gas feeding direction, whereas the other end is disposedaway from the tube sheet in the upstream side in the mixed-gas feedingdirection.

According to the invention in this section the film member wrappedaround the hollow fiber bundle regulates feeding of a permeate gas in adirection opposite to a direction of feeding a mixed gas (detailedlater), therefore gas separation can be more efficiently conducted inthe bore feed type module.

Embodiment in Section E

There will be described one embodiment of the invention in this sectionwith reference to the drawings. FIG. 17 is a cross-sectional viewschematically showing a basic configuration of a gas separation membranemodule according to this embodiment.

A gas separation membrane module 601 as shown in FIG. 17 is of the borefeed type, which has a hollow fiber bundle 615 as a collection of anumber of hollow fiber membranes 614, a casing 610 housing the bundle,and tube sheets 621 and 622 at both ends of the hollow fiber bundle 615.

The hollow fiber membrane 614 can be made of any known structure as longas it has gas separation ability. For example, it is suitably made ofpolymer material which is glassy at normal temperature (23° C.) such as,in particular, polyimide, polysulfone, polyetherimide, polyphenyleneoxide and polycarbonate for their gas separation ability.

The hollow fiber bundle 615 can be, for example, a collection of about100 to 1,000,000 hollow fiber membranes 614. There are no particularrestrictions to the shape of the collected hollow fiber bundle 615, butfor example, the cylindrical shape is preferable in the light ofeasiness in production and pressure resistance of a vessel. FIG. 17shows an embodiment in which hollow fiber membranes 614 are disposedsubstantially in parallel, however, these hollow fiber membranes can becross-arranged.

There are no particular restrictions to mixed gas to be subjected toseparation by the hollow fiber membrane 614, but it can be, for example,a mixed gas of a more permeable gas and a less permeable gas with aratio of permeation rates to a separation membrane of 2 or more. The gasseparation membrane module 601 of this embodiment can be use forseparating a particular gas component from a mixed gas in variousmanners. For example, it can be used for drying a variety of gases,humidification of a variety of gases, nitrogen enrichment or oxygenenrichment.

The tube sheets 621, 622 are formed as a disc-shape in response to thecross-sectional shape of the casing, and they hold the end of the hollowfiber bundle 615 with each hollow fiber membrane 614 opened. The tubesheets 621, 622 can be made of a thermoplastic resin such aspolyethylene and polypropylene or a thermosetting resin such as an epoxyresin and a urethane resin. The tube sheets 621, 622 have a function ofbundling the hollow fiber membranes 614 together. It also has a functionof sealing between the hollow fiber membranes 614 as well as between thehollow fiber bundle 615 and the inner surface of the casing 610. Asshown in FIG. 17, a closed space 618 (as described later, having apermeate gas outlet 610 c) is formed by the casing 610 and two tubesheets 621 and 622, into which the permeate gas from the hollow fibermembrane 614 is to be introduced. A mixed gas space 619 a is formed bythe casing 610 and the tube sheet 621, while a non-permeate gas space619 b is formed by the casing 610 and the tube sheet 622. Other sealingmeans can be installed for sealing between the tube sheets 621, 622 andthe inner surface of the casing 610.

For a nitrogen membrane module, the epoxy resin for example described inJapanese published examined application No. 1990-36287 can be used forthe tube sheet 621, 622, whereas for an organic-vapor separation modulethe epoxy resin for example described in WO 2009/044711 can be used. Theepoxy resin as disclosed in section B can also be used for a tube sheetin the module of this section

As shown in FIG. 17, the casing 610 is substantially cylindrical as awhole. The casing 610 has a mixed gas inlet 610 a in the upstream side(left side in the figure) for introducing mixed gas into the casing 610,a non-permeate gas outlet 610 b in the downstream side (right side inthe figure), and a permeate gas outlet 610 c in its side wall. Thenumber of the permeate gas outlet 610 c can be one or two or more.Permeate gas outlets 610 c can be disposed at regular intervals alongthe side wall of the casing 610. The permeate gas outlet 610 c is, inthis example, placed at the position near the upstream tube sheet 621(specifically, the position of exposed part A1 in the hollow fiberbundle 615 without a film member 631 described later).

The mixed gas introduced from the mixed gas inlet 610 a enters into eachhollow fiber membrane 614 via the end face of the tube sheet 621 andflows downstream in the inside. A part of the mixed gas permeates thehollow fiber membrane 614 and the permeate gas is fed into the inside ofthe closed space 618 and then discharged from the casing through thepermeate gas outlet 610 c. On the other hand, a non-permeate gas notpermeating the hollow fiber membrane as it is flows downstream in thehollow fiber membrane 614 and flows outward from the end face, and thenis discharged out of the casing through the non-permeate gas outlet 610b.

Although FIG. 17 schematically shows the casing 610, the casing can havea configuration as shown in FIG. 19. The casing 610 in this example hasa cylindrical member 611 with open ends and caps 612, 613 attached tothe ends. The tubular member 611 and the caps 612, 613 can be, forexample, made of a metal, a plastic or a ceramic. A mixed gas inlet 610a and a non-permeate gas outlet 610 b are formed in the caps 612 and613, respectively. For example, the mixed gas inlet 610 a and thenon-permeate gas outlet 610 b can be formed at the center of the caps612, 613 (center seen from a front of the cap), respectively.

A film member 631 is wrapped around the periphery of the hollow fiberbundle 615, as shown in FIGS. 17 and 18, in the gas separation membranemodule 601 of this embodiment. The end 631 a of the film member 631substantially abuts on the tube sheet 622, while the other end 631 b isdisposed away from the tube sheet 621 by a predetermined distance. Theregion of hollow fiber bundle 615, which is not covered by the filmmember 631, is indicated by symbol A1 (exposed part) in FIG. 17. Thefilm member 631 can cover 50% to 95%, preferably 75% to 92% of the outersurface of the hollow fiber bundle. Alternatively, the film member 631may cover the whole surface of the hollow fiber bundle so that each endof the film member are close to each tube sheet, and one or multipleopenings are formed on the film member 631 in the vicinity of the tubesheet 621.

The phrase, (an end of a film member) “substantially abut” means boththat (i) the film end completely abuts on the tube sheet, and that (ii)the film end is close to the tube sheet with a small gap between thefilm end and the tube sheet due to convenience in production forexample. When the tube sheet is made of an epoxy resin or the like andthe film end is inserted in the tube sheet (for example, a case in whichthe film end is inserted in the tube sheet material and then the tubesheet is cured), the tube sheet may be cracked or damaged beginning atthe part. Thus it may be preferable to arrange the film so that the endis not inserted into the tube sheet.

The film member 631 can be made of any material as long as the materialis substantially gas-impermeable. The term “substantiallygas-impermeable” means that: the gas permeability of the film member 631is low enough to limit gas flow. For example, it can be a plastic filmsuch as polyimide, polyethylene, polypropylene, polyamide and polyester.Among these, polyimide is preferable in the light of heat resistance,solvent resistance and processability. In addition to a plastic film, ametal foil such as aluminum and stainless steel can be used. A thicknessof the film can be in the range of several ten μm to several mm. Thefilm member 631 can be formed by attaching both side edges of the sheetto form cylindrical shape, or the film member 631 can be of a seamlesstubular member. Side edges of the film can be attached by for exampleadhesive material or tape.

If the module does not has the film member 631, permeate gas from thehollow fiber membrane 614 flows in a cross-flow direction as shown byarrow 13 in FIG. 18 (i.e. a direction crossing the hollow fiber membrane614). On the other hand, when the film member 631 is wrapped on thehollow fiber bundle 615 as in this embodiment, diffusion of the permeategas is prevented and thus the permeate gas flows along thecountercurrent direction f2 to the direction of mixed gas feeding f1.

There will be described an exemplary method for using the separationmembrane module of this embodiment constructed as described above. Amethod for using the module according to embodiment is not limited tothe following example.

First, a mixed gas is introduced through the mixed gas inlet 610 a intothe mixed gas space 619 a within the casing 610. The introduced mixedgas enters each hollow fiber membrane 614 from the end face of the tubesheet 621, and flows downstream inside of the membrane. It is preferablethat pressure within the hollow fiber membrane 614 is higher than thatof the closed space 618, specifically, it is suitable that the mixed gasis fed at a pressure of 0.01 MPaG to 10 MPaG whereas the closed space618 is vacuumed. A part of the mixed gas selectively permeates thehollow fiber membrane 614 during this operation, and is then dischargedinto the closed space 618 outside of the hollow fiber membrane 614. Onthe other hand, the non-permeable gas flows downstream as it is withinthe hollow fiber membranes 614 and then discharged to the non-permeategas space 619 b outside of the hollow fiber membranes 614 from the endface downstream.

The permeate gas from the hollow fiber membrane 614 is then introducedinto the closed space 618 in the casing 610. The film member 631prevents the permeate gas from diffusing in the region wrapped with thefilm member 631, as shown in FIG. 18, thus the permeate gas flows alongthe direction of the arrow 12 opposite to the direction of feeding themixed gas ft. The permeate gas is then discharged out of the casing 610through the permeate gas outlet 610 c (see FIG. 17). The non-permeategas is released from the downstream end of the hollow fiber membrane 614and then discharged outside via the non-permeate gas outlet 610 b.

According to the separation membrane module 601 described above, thefilm member 631 can prevent the permeate gas from diffusing and enablesthe permeate gas to flow along the direction opposite to the directionof feeding a mixed gas. Thus, gas separation efficiency can be improved.

The inventions according to section E are as follows.

[1] A gas separation membrane module comprising;

a hollow fiber bundle as collection of a number of hollow fiber membranewith gas separation ability,

a casing having a mixed gas inlet, a permeate gas outlet and anon-permeate gas outlet, in which said hollow fiber bundle is disposed,and

two tube sheets for fixing both ends of said hollow fiber bundle,

in which mixed gas from said mixed gas inlet is fed into said hollowfiber membrane, while the mixed gas partly permeates the membrane, toachieve gas separation,

wherein,

(i) a structure for feeding purge gas is not provided, said purge gas isfor purging permeate gas from hollow fiber membrane, and

(ii) the module further comprising, a gas-impermeable film memberwrapped around the outer surface of said hollow fiber bundle, in whichone end substantially abuts on said tube sheet in the downstream sidealong the mixed-gas feeding direction, whereas the other end is disposedaway from the tube sheet in the upstream side in the mixed-gas feedingdirection.

[2] The gas separation membrane module as described in [1], wherein saidone end of the film member is configured not to be inserted into saidtube sheet.

[3] The gas separation membrane module as described in [1] or [2],wherein said permeate gas outlet is formed in a part of said casing, thepart surrounding an exposed area of said hollow fiber bundle where thebundle is not covered by said film member.

[4] The gas separation membrane module as described in any of [1] to[3], wherein said film member covers 50% to 95% of the outer surface ofsaid hollow fiber bundle in the region between the one tube sheet andthe other tube sheet.

[5] The gas separation membrane module as described in any of [1] to[4], wherein said film member is made of polyimide.

Section F: Gas Separation Membrane Module in which Gas Leakage from aGap Between a Film End and a Tube Sheet is Prevented

Technical Field

The invention in this section relates to a gas separation membranemodule for gas separation using hollow fiber membranes, in particular,to a bore feed type gas separation membrane module which can prevent gasleakage from a gap between a film end and a tube sheet to achieve moreefficient gas separation.

Background Art

A hollow fiber type gas separation membrane module generally has ahollow fiber element having a hollow fiber bundle including a number ofhollow fiber membranes with selective permeability and a hollow casinghousing the element. Both ends or one end of the hollow fiber bundle inthe hollow fiber element are fixed by a resin-cured plate (tube sheet).The casing has a mixed gas inlet, a permeate gas outlet and anon-permeate gas outlet.

For the purpose of efficient gas separation, for example, Japanesepublished unexamined application No. 2000-262838 discloses a gasseparation membrane as a so-called bore feed type module in which amixed gas is fed into hollow fiber membranes, wherein a part of thehollow fiber bundle is covered by a film member and carrier gas outsideof the hollow fiber membranes and the mixed gas in side of the membranesflow countercurrently.

In the above gas separation membrane module in the reference document,the flow direction of the carrier gas can be regulated to achieve moreefficient gas separation, however, it is important to improve anefficiency of gas separation even in a module without using carrier gas(purge gas). To improve the efficient of gas separation, it is effectiveto prevent gas from leaking through the gap between the film end and thetube sheet (detailed later) whether purge gas is used or not.

In view of the above problem, an objective of this section is to providea bore type gas separation membrane module capable of separating gasesby preventing gas leakage from a gap between a film end and a tubesheet.

The summary of the main invention disclosed in this section is asfollows.

[1] A gas separation membrane module comprising;

a hollow fiber bundle as a collection of a number of hollow fibermembrane with gas separation ability,

a casing having a mixed gas inlet, a permeate gas outlet and anon-permeate gas outlet, in which said hollow fiber bundle is disposedand

two tube sheets for fixing both ends of said hollow fiber bundle,

a gas-impermeable (including substantially gas-impermeable) film memberwrapped around the outer surface of said hollow fiber bundle, in whichone end substantially abuts on said tube sheet in the downstream sidealong the mixed-gas feeding direction, whereas the other end is disposedaway from said tube sheet in the upstream side in the mixed-gas feedingdirection, and a sealing structure sealing a gap between said one end ofthe film member and said tube sheet.

According to the invention in this section, there can be provided a boretype gas separation membrane module capable of separating gases bypreventing gas leakage from a gap between a film end and a tube sheet.

Embodiments in Section F

There will be described one embodiment of the invention in this sectionwith reference to the drawings. FIG. 21 shows the shape of a casing(detailed later) more specifically as an example.

A gas separation membrane module (hereinafter, simply referred to as“module”) 801 shown in FIGS. 20 and 21 has a hollow fiber bundle 815 asa collection of a number of hollow fiber membranes 814, a casing 810housing the bundle, and tube sheets 821, 822 at the ends of the hollowfiber bundle 815. This module 801 is of a so-called bore feed type,where the mixed gas (source gas) is fed into the hollow fiber membrane814.

The hollow fiber membrane 814 can be made of any of known structure aslong as it has gas separation ability. For example, it is suitably madeof polymer material, which is glassy at normal temperature (23° C.) suchas, in particular, polyimide, polysulfone, polyetherimide, polyphenyleneoxide and polycarbonate for the gas separation ability.

The hollow fiber bundle 815 can be, for example, a collection of about100 to 1,000,000 hollow fiber membranes 814. There are no particularrestrictions to the shape of the collected hollow fiber bundle 815,however, a cylindrical shape is preferable in the light of easiness inproduction and pressure resistance of a vessel. Although FIG. 20 showsan embodiment in which hollow fiber membranes 814 are disposedsubstantially in parallel, these hollow fiber membranes can becross-arranged.

There are no particular restrictions to a mixed gas to be subjected toseparation by the hollow fiber membrane 814, however it can be, forexample, a mixed gas of a more permeable gas and a less permeable gaswith a ratio of permeation rates to a separation membrane of 2 or more.The gas separation membrane module 801 of this embodiment can be use forseparating a particular gas component from a mixed gas in variousmanners. For example, it can be used for drying a variety of gases,humidification of a variety of gases, nitrogen enrichment or oxygenenrichment.

The tube sheets 821, 822 are formed substantially as a disc-shape inresponse to the shape of the casing 810, and fix the end of the hollowfiber bundle 815 with each hollow fiber membrane 814 opened. The tubesheets 821, 822 can be made of a thermoplastic resin such aspolyethylene and polypropylene or a thermosetting resin such as an epoxyresin and a urethane resin. The tube sheets 821, 822 have a function ofbundling the hollow fiber membranes 814 together. It also has a functionof sealing between the hollow fiber membranes 814 as well as between thehollow fiber bundle 815 and the inner surface of the casing 810. Asshown in FIG. 20, a closed space 818 (as described later, having apermeate gas outlet 810 c) is formed by the casing 810 and two tubesheets 821 and 822, the permeate gas from the hollow fiber membrane 814is to be introduced into the closed space 818. A mixed gas space 819 ais formed by the casing 810 and the tube sheet 821, whereas anon-permeate gas space 819 b is formed by the casing 810 and the tubesheet 822. Another sealing means can be used for sealing between thetube sheets 821, 822 and the inner surface of the casing 810.

For a nitrogen membrane module, the epoxy resin for example described inJapanese published examined application No. 1990-36287 can be used forthe tube sheet 821, 822, whereas for an organic-vapor separation modulethe epoxy resin for example described in WO 2009/044711 can be used. Theepoxy resin as disclosed in section B can also be used for a tube sheetin the module of this section

The casing 810 is substantially cylindrical as a whole as shown in FIG.20. The casing 810 has a mixed gas inlet 810 a for introducing a mixedgas into the casing 810 in the upstream side (left side in the figure),a non-permeate gas outlet 810 b in the downstream side (right side inthe figure) and a permeate gas outlet 810 c in its side wall. The numberof the permeate gas outlet 810 c can be one or two or more. The permeategas outlets 810 c can be disposed at regular intervals along the sidewall of the casing 810. The permeate gas outlet 810 c in this example isformed at the position near the upstream tube sheet 821 (specifically,the position of exposed part A1 in the hollow fiber bundle 815 without afilm member 831 described later).

The mixed gas introduced from the mixed gas inlet 810 a is fed into eachhollow fiber membrane 814 from the end face of the tube sheet 821, andflows downstream in the inside of the membrane. A part of the mixed gaspermeates the hollow fiber membrane 814, and the permeate gas is fed tothe inside of the closed space 818 and then discharged from the casingthrough the permeate gas outlet 810 c. On the other hand, a non-permeategas not permeating the hollow fiber membrane as it is flows downstreamin the hollow fiber membrane 814 and flows outward from the end face,and then is discharged out of the casing through the non-permeate gasoutlet 810 b.

The mixed gas inlet 810 a and/or the non-permeate gas outlet 810 b canbe disposed in such a way that their central axes are aligned with thecentral axis of the casing 810 (that is, the central axis of the hollowfiber bundle 815). The casing 810 can have a cylindrical member 811 andretaining members 813 for hold the tube sheet at its ends (one is notshown) as in the example in FIG. 21(A). The tubular member 811 and theretaining member 813 can be welded to each other. The inner surface ofthe retaining member 813 in this example has a straight part 813 a witha constant diameter, a large diameter part 813 b with a larger diameterthan the straight part 813 a, and a tapered part 813 c with a graduallyreduced diameter. The tube sheet 822 has as shown in FIG. 21(A) ahollow-fiber-membrane burying part 822 a into which the part of hollowfiber membrane 814 is placed, and a surrounding part 822 b in which thehollow fiber membrane 814 does not exist.

A film member 831 is wrapped around the peripheral surface of the hollowfiber bundle 815 in the gas separation membrane module 801 of thisembodiment as shown in FIGS. 20 and 21. One end 831 a of the film member831 (hereinafter, also referred to as “film end 831 a.”) is close to thetube sheet 822, whereas the other end 831 b is disposed away from thetube sheet 821 by a predetermined distance. In FIG. 20, the region ofhollow fiber bundle 815, which is not covered by the film member 831, isindicated by symbol A1 (exposed part). The film member 831 can cover 50%to 95%, preferably 70% to 92% of the outer surface of the hollow fiberbundle. Alternatively, the member can cover the whole surface of thehollow fiber bundle so that each end of the film member 831 is close toeach tube sheet, and the film member 831 can has one or multipleopenings in the vicinity of the tube sheet 821.

The film member 831 can be made of any material as long as the materialis substantially gas-impermeable. The term “substantiallygas-impermeable” means that: the gas permeability of the film member 631is low enough to limit gas flow. For example, it can be a plastic filmsuch as polyimide, polyethylene, polypropylene, polyamide and polyester.Among these, polyimide is preferable in the light of heat resistance,solvent resistance and processability. In addition to a plastic film, ametal foil such as aluminum and stainless steel can be used. A thicknessof the film can be in the range of several ten μm to several mm.

The film member 831 can be formed by attaching both side edges of a filmto form the cylindrical shape, or the member 631 can be of a seamlesstubular member. The edges of the film can be attached for example byadhesive material or tape.

If the tube sheet is epoxy resin and the film end is buried in the tubesheet (e.g. a case in which the film end is inserted into the materialand then cured), the tube sheet may be cracked or damaged beginning atthe part. To avoid this, the film end is not buried in the tube sheet inthis embodiment. In this configuration, however, a gap A31 might beformed between the film end 831 a and the tube sheet 822 as shown inFIG. 21 (for illustrative purposes, the size of the gap A31 isexaggerated).

A sealing structure 850 for sealing the gap A31 between the film end 831a and the tube sheet 822 is provided as shown in FIGS. 20 and 21 in thisembodiment. The sealing structure 850 in this example has twocylindrically formed sealing parts 851 and 853 (see FIG. 21), which aredisposed on both surfaces of the film to sandwich the film 831 a andwrap the hollow fiber bundle 815.

Both sealing parts 851, 853 are made of material into which liquid resinmaterial such as epoxy resin can permeate, that is, the material havinga predetermined capillary force. The sealing parts 851, 853 can be madeof any material as long as it has such feature, thus for example a meshmember formed by interweaving fibers, such as cloth or net can be used.The fiber can be, for example, a chemical or natural fiber, and a glassfiber or a carbon fiber can be used.

As shown in FIG. 21, the first sealing part 851 is disposed on the outersurface of the film member 831, whereas the second sealing part 853 isdisposed on the inner surface of the of the film member 831. Each of thesealing parts 851, 853 is disposed such that it extends from the filmend 831 a toward the side of the tube sheet 822. A part of the extensionof each of the sealing parts 851, 853 is buried in the intact part 822 bin the tube sheet 822.

A fixing tape 855 is attached to the sealing part 851 to fix the part851 to the film member 831 as shown in FIG. 21(A). The fixing tape 855can be applied for example such that it surrounds the outercircumference of the hollow fiber bundle 815. The fixing tape 855 canalso be wrapped around the fixing tape 855 twice or more. Instead, thetape 855 can be applied only on a part of the outer circumference.

An overlap portion of the sealing parts 851, 853 can be fixed to eachother by a fixture 857 as shown in FIG. 21(B). The fixture 857 can be amechanism for mechanically fixing both members, such as staple(s). Inaddition, for example, yarn or wire can be employed.

The sealing parts 851, 853 work to prevent leakage of a permeate gasfrom the gap A31 as described later. To prevent the leakage moreeffectively, at least some area of the sealing parts 851 and 853, whichis to face the gap A31, can be permeated with cured resin material. Sucha configuration can provide the sealing parts 851, 853 with improvedgas-impermeable property, resulting in prevention of gas leakage. Theconfiguration can be applied to only one sealing part 851 or 853.

The film member 831 and the sealing structure 850 can be produced forexample as follows. The process described below is only an example andthe process sequence and the like do not limit the present invention inany manner.

First, the hollow fiber bundle 815 and the casing (for example, that inFIG. 21) are prepared. The single film member 831 formed in apredetermined size is also prepared. The sealing parts 851, 853 are thenput on both side of the film edge such that the region near the end 831a is sandwiched. The overlap portions of the sealing parts 851, 853 isfixed by a stapler (one example).

Next, the film member 831 in the above state is wrapped around thehollow fiber bundle 815 and then fixed to each other by a tape (notshown). Then, the hollow fiber bundle 815 is positioned at apredetermined position in the casing 810, and the tube sheets 821, 822are formed at the ends of the hollow fiber bundle 815. The tube sheets821, 822 can be formed by filling the end of the hollow fiber bundle 815with an epoxy material and then curing the material.

A specific embodiment will be described with reference to the example inFIG. 21. The filling of the epoxy material can be conducted, forexample, while the casing 810 for the hollow fiber bundle 815 issupported in a vertical direction, with a mold (not shown) attached tothe lower end of the casing. During this process, the surface level ofthe epoxy material to be applied is controlled such that the ends of thesealing parts 851, 853 are buried in the tube sheet 822 as shown in FIG.21(A), whereas the end 831 a is not buried. Once the ends of the sealingparts 851, 853 are immersed in the epoxy material, the epoxy materialinfiltrates into the sealing parts 851, 853 (a region including at leasta part facing the gap A31) by the capillary force.

Then, the tube sheet material is cured, and the cured tube sheet 822 iscut at a predetermined position to open the hollow fiber membrane 814.Subsequently, a conventional assembling (for example, a process forproducing the casing 810) is conducted to form a module if necessary.

The film member 831 and the sealing parts 851, 853 can be disposed inthe following order. First, the second sealing part 853 is wrapped onthe hollow fiber bundle 815, then the film member 831 is wrapped, andthe first sealing part 851 is wrapped.

There will be described an example of the used of the separationmembrane module of this embodiment having the above configuration. Themethod for using a module according to this embodiment is not limited tothe following.

First, the mixed gas is introduced into the mixed gas space 819 a in thecasing 810 via the mixed gas inlet 810 a. The introduced mixed gas isfed into each hollow fiber membrane 814 from the end face of the tubesheet 821 and flows downstream in the inside. It is preferable that thepressure in the hollow fiber membrane 814 is higher than a pressure inthe closed space 818; for example, it is suitable to feed a mixed gas ata pressure of 0.01 MPaG to 10 MPaG, and to vacuum the closed space, forexample. During this operation, a part of the mixed gas selectivelypermeates the hollow fiber membrane 814 and is discharged to the closedspace 818 outside of the hollow fiber membrane 814. On the other hand, anon-permeate gas as it its flows downstream in the hollow fiber membrane814 and discharged from the downstream end face to the non-permeate gasspace 819 b outside of the of the hollow fiber membrane 814.

If the module does not have the film member 831, the permeate gas fromthe hollow fiber membrane 814 flows along a cross-flow direction (thatis, a direction crossing the hollow fiber membrane 814). Alternatively,the gas flows along f4 direction, which includes the opposite directionrelative to f2, that is, in a parallel flow direction, and finally 13 asshown by an arrow f3 in FIG. 21(B). On the other hand, according to thisembodiment, since the film member 831 is wrapped on the hollow fiberbundle 815, dissipation of a permeate gas is prevented and the permeategas flows in a direction of an arrow 12, that is, a countercurrentdirection to the direction of mixed gas feeding f1, resulting in animproved efficiency of gas separation. In particular, this embodimenthas the sealing structure 850 for sealing the gap A31, therefore leakageof the permeate gas through this gap A31 is prevented. Accordingly,dissipation of the permeate gas can be reliably prevented and gasseparation can be more efficiently conducted.

Leakage of the permeate gas can be also prevented by a structure inwhich the film end 831 a is directly buried in the tube sheet 822, butit may cause cracks or breakage beginning the area near the film end 831a in the tube sheet 822. In contrast, since the sealing parts 851, 853as a separate member from the film member 831 are buried in thisembodiment, such cracks and breakage in the tube sheet 822 can beprevented by appropriately selecting a material for the sealing part.

As described above, even when the sealing parts 851, 853 are made of amesh material the leakage of the permeate gas can be prevented comparedwith configuration with no sealing part. However, according to thisembodiment, leakage of a permeate gas can be more reliably prevented,since a resin material infiltrates into the sealing parts 851, 853 andcured therein.

Other Embodiments

Although one embodiment of the invention in this section has beendescribed, the invention in this section is not limited to the above veembodiment, but various changes can be made.

For example, the module can have only one of the first and the secondsealing parts 851, 853. Alternatively, the fixing tape 855 for fixingthe first sealing part 851 to the film member 831 can be omitted.Furthermore, the fixture 857 for fixing the overlap of two sealing parts851, 853 (see FIG. 21(B)) can be omitted.

FIG. 22 shows another sealing structure; FIG. 22(A) is a schematiccross-sectional view of the whole module and FIG. 22(B) is an enlargedpartial view of the figure. In this example, filler 891 is illustrateddisposed such that it fills a gap A31 between a film member 831 and atube sheet 822. The filler 891 can be resin material such asheat-resisting silicone injected such that it surrounds the film member831. Such a filler 891 can also prevent the permeate gas from leakingfrom the gap A31, consequently, a module capable of conducting efficientgas separation can be obtained. The filler 891 can be formed byprocesses such as forming one or multiple holes on the side wall of thecasing after forming the tube sheet 822 in the casing, and theninjecting the filler 891 and curing the filler.

Position for placing the filter 891 is not limited to the position shownin FIG. 22. For example, the filler 893 can be disposed at a positionaway from the gap A31 by a predetermined distance, between the filmmember 831 and the casing 810 as shown in FIG. 23. The filler 893 can bedisposed at one position in the longitudinal direction of the filmmember 831 as shown in FIG. 23. Such a filler 893 can be disposed aroundthe periphery of the film member 831 to thereby block gas flow, and itswidth can be for example about 3 mm to 5 mm (for example, 0.5% of theouter surface of the film) or more.

Alternatively, filler surrounding the periphery of the film member 831can be formed over further wider (longer) region to fill the gap betweenthe film member 831 and the casing 810; for example, 10% or more of theouter surface of the film member can be covered with the filler.

A gas separation membrane module of the invention in this section canhave a structure for allowing a purge gas to flow as shown in FIG. 24.This gas separation membrane module has a hollow fiber bundle 915, acasing 910, two tube sheets 921, 922 for fixing the ends of the hollowfiber bundle 915, a gas-impermeable film member 931 wrapped on the outersurface of the of the hollow fiber bundle and a sealing structure 950for sealing a gap between the end of the film member 931 and the tubesheet 922. This gas separation membrane module further has a core tube971 for feeding a purge gas.

The casing 910 has a mixed gas inlet 910 a in the upstream side (leftside in the figure) and a permeate gas outlet 910 c in the sidewall asin the module in FIG. 20. The structure in the downstream side from thetube sheet 922 is slightly different from the module in FIG. 20, thatis, a non-permeate gas outlet 910 b is formed in the side wall of thecasing 910 and a core tube 971 is inserted in the center of the casing910.

The core tube 971 is a member in which one of the ends is closed whereasthe other is open, and the tube is disposed along a direction that theopening is downstream (the side of the tube sheet 922). The core tube971 extends penetrating the tube sheet 922 and its tip is buried in thetube sheet 921 in the upstream side. The core tube 971 has hole(s) 971 ain a region between two tube sheets 921, 922.

The principle for gas separation principle in the module is basicallythe same as that shown in FIG. 20. A purge gas is fed from the opening(purge gas inlet 910 d) into the core ore tube 971, and the purge gas isdischarged into the closed space 918 in the casing 910 via the hole 971a. The purge gas flows along the direction of f2 (a countercurrentdirection to the direction of feeding a mixed gas) among the hollowfiber membranes 914, and then the purge gas pushes the permeate gasdischarged into the space towards the permeate gas outlet 910 c, whichaccelerates discharge of the permeate gas.

It is also preferable that in such a module utilizing a purge gas, asealing structure 950 for sealing a gap between the film member 931 andthe tube sheet 922 is formed. The sealing structure 950 can be any ofvarious structures described above. Thus, leakage of the permeate gasand purge gas from the gap can be prevented, and then the permeate gasand purge gas can smoothly flow in the f2 direction, as a result, moreefficient gas separation is accomplished.

The summary of the main invention disclosed in section F is as follows.

[1] A gas separation membrane module comprising;

a hollow fiber bundle as a collection of a number of hollow fibermembrane with gas separation ability,

a casing having a mixed gas inlet, a permeate gas outlet and anon-permeate gas outlet, in which said hollow fiber bundle is disposed,and

two tube sheets for fixing both ends of said hollow fiber bundle,

a gas-impermeable (including substantially gas-impermeable) film memberwrapped around the outer surface of said hollow fiber bundle, in whichone end substantially abuts on said tube sheet in the downstream sidealong the mixed-gas feeding direction, whereas the other end is disposedaway from said tube sheet in the upstream side in the mixed-gas feedingdirection, and

a sealing structure sealing a gap between said one end of the filmmember and said tube sheet.

[2] The gas separation membrane module as described in [1], wherein saidsealing structure comprises;

a sealing part wrapped on the inside or the outside in a radialdirection of said film member at said one end of said film member, thesealing part extending from said end toward said tube sheet, a part ofthe extending portion is buried in said tube sheet.

[3] The gas separation membrane module as described in [2], comprising,as said sealing part,

the first sealing part made of a member, into which liquid resinmaterial can permeate, which is wrapped on the outside in the radialdirection of said film member, and

the second sealing part made of a material, into which liquid resinmaterial can permeate, which is wrapped on the inside in the radialdirection of said film member.

[4] The gas separation membrane module as described in [2] or [3],wherein said sealing part is a mesh member.

[5] The gas separation membrane module as described in [3] or [4],wherein in at least a region facing said gap of said sealing parts, aresin material permeates and is cured to seal said gap.

[6] The gas separation membrane module as described in [3], wherein saidsealing structure further comprises a fixing tape for fixing said firstsealing part to said film member.

[7] The gas separation membrane module as described in [3], wherein saidsealing structure further comprises a fixture for securing an extendingportion of said first sealing part extending from said one end of thefilm member to an extending portion of said second sealing partextending from said one end of the film member.

[8] The gas separation membrane module as described in [1], wherein saidsealing structure comprises a filler disposed such that the filler fillssaid gap between said one end of the film member and said tube sheet.

[9] The gas separation membrane module as described in any of [1] to[8], wherein extending portion of said one end of the film member isconfigured to not to be inserted into said tube sheet.

[10] The gas separation membrane module as described in any of [1] to[9], wherein said film member is made of polyimide.

Section G: Gas Separation Membrane Module Ensuring Adequate SealingPerformance Near a Tube Sheet

Technical Field

This invention relates to a gas separation membrane module for gasseparation using a hollow fiber membrane, in particular, to a gasseparation membrane module which ensures adequate sealing in thevicinity of a tube sheet and therefore it can be used at hightemperature satisfactorily, even when a tube sheet material relativelysusceptible to cure shrinkage is used

Background Art

A hollow fiber type gas separation membrane module generally has ahollow fiber element including a hollow fiber bundle comprising a numberof hollow fiber membranes with selective permeability and a hollowcasing housing the element. The hollow fiber bundle is fixed at its oneor two ends by a resin cured plate (tube sheet).

A gas separation membrane generally has a larger gas permeation rate ata higher temperature and a higher pressure of a supplied gas. Therefore,when using the gas separation membrane module, it may be considered thatthe source gas is compressed by for example a compressor before beingfed to the module. In some cases, the compressed gas may be warmed toabout 149° C. to 260° C.

It is necessary to use heat-resistant tube sheet material in suchmodules for separating high-temperature mixed gas as described above.However, such tube sheet material is generally susceptible to cureshrinkage during its curing, thus there may be a problem such asinadequate performance of sealing around the tube sheet. In view of theproblem, an objective of the invention in this section is to provide aseparation membrane module and so on which ensures adequate sealingperformance in the vicinity of the tube sheet and therefore it can beused at high temperature satisfactorily, even when a tube sheet materialrelatively susceptible to cure shrinkage is used and furthermore

The summary of the main invention disclosed in this section is asfollows.

A gas separation membrane module according to one embodiment of theinvention in this section comprises;

a hollow fiber bundle as a collection of a number of hollow fibermembranes with gas separation ability,

a casing housing said hollow fiber bundle, and

a tube sheet for fixing at least one end of said hollow fiber bundle,

wherein the outer surface of said tube sheet does not contact the innersurface of said casing,

further comprising a sealing member for sealing between the outersurface of said tube sheet and the inner surface of said casing.

A process for manufacturing a gas separation membrane module accordingto one embodiment of the invention in this section is a process formanufacturing a gas separation membrane module, comprising a hollowfiber bundle as a collection of a number of hollow fiber membranes withgas separation ability, a casing housing said hollow fiber bundle, and atube sheet for fixing at least one end of said hollow fiber bundle,comprising

applying a mold release to at least a part which is to be in contactwith said tube sheet in the inner surface of said casing,

filling a thermosetting resin in a part of said casing,

curing said thermosetting resin to form said tube sheet, and

forming, after said curing of said thermosetting resin, a sealing memberbetween the outer surface of said tube sheet and the inner circumferencesurface sure of said casing.

Definitions of terms used herein are as follows.

The term, “high-temperature condition” or “high temperature” means atemperature in the range of, for example, 80° C. to 300° C.

The term, “cylindrical vessel” is not limited to those in which bothends are open, but includes those in which only one end is open.

According to the invention in this section, there is provided a gasseparation membrane module which ensures adequate sealing in thevicinity of the tube sheet even when the tube sheet material relativelysusceptible to cure shrinkage is used and furthermore which can besatisfactorily used at high temperature.

Embodiments in Section G

There will be described one embodiment of the invention in this sectionwith reference to the drawings. FIG. 25 more specifically shows theshape of a casing (detailed later) as an example. The configurationsdescribed below are merely examples and a gas separation membrane moduleof the present invention is not limited to these configurations.

A gas separation membrane module (hereinafter, simply referred to as“module”) 1001 shown in FIGS. 25 and 26 has a hollow fiber bundle 1015as a collection of a number of hollow fiber membranes 1014, a casing1010 housing the bundle and tube sheets 1021, 1022 at the ends of thehollow fiber bundle 1015. This module 1001 is, for example, of aso-called bore feed type where a mixed gas (source gas) is fed into thehollow fiber membrane 1014.

The hollow fiber membrane 1014 can be made of any of known structure aslong as it has gas separation ability. For example, it is suitably madeof polymer material, which is glassy at normal temperature (23° C.) suchas, in particular, polyimide, polysulfone, polyetherimide, polyphenyleneoxide and polycarbonate for the gas separation ability.

The hollow fiber bundle 1015 can be, for example, a collection of about100 to 1,000,000 hollow fiber membranes 1014. There are no particularrestrictions to the shape of the collected hollow fiber bundle 1015, butfor example, a cylindrical shape is preferable in the light of easinessin production and pressure resistance of a vessel. FIG. 25 shows anembodiment in which hollow fiber membranes 1014 are disposedsubstantially in parallel, however, these hollow fiber membranes can becross-arranged.

There are no particular restrictions to a mixed gas to be subjected toseparation by the hollow fiber membrane 1014, but it can be, forexample, a mixed gas of a more permeable gas and a less permeable gaswith a ratio of permeation rates to a separation membrane of 2 or more.The gas separation membrane module 1001 of this embodiment can be usefor separating a particular gas component from a mixed gas in variousmanners. For example, it can be used for drying a variety of gases,humidification of a variety of gases, nitrogen enrichment or oxygenenrichment.

The tube sheets 1021, 1022 are formed substantially as a disc-shape(detailed later) in response to the shape of the casing 1010, and fixthe end of the hollow fiber bundle 1015, with each hollow fiber membrane1014 opened. In this example, the tube sheet works as a sealer betweenthe hollow fiber membranes. The tube sheet can be made of athermoplastic resin such as polyethylene and polypropylene or athermosetting resin such as an epoxy resin and an urethane resin. Therewill be described a case in which a tube sheet is made of athermosetting resin.

For a nitrogen membrane module, the epoxy resin for example described inJapanese published examined application No. 1990-36287 can be used forthe tube sheet 1021, 1022, whereas for an organic-vapor separationmodule the epoxy resin for example described in WO 2009/044711 can beused The epoxy resin as disclosed in section B can also be used for atube sheet in the module of this section.

A closed space 1018 (having a permeate gas outlet 1010 c as describedbelow) is formed by the casing 1010 and the two tube sheets 1021, 1022as shown in FIG. 25 in this embodiment. The permeate gas permeating thehollow fiber membrane 1014 is introduced into this closed space 1018. Amixed gas space 1019 a is formed by the casing 1010 and the tube sheet1021, whereas a non-permeate gas space 1019 b is formed by the casing1010 and the tube sheet 1022.

As shown in FIG. 25, the casing 1010 is substantially cylindrical as awhole. The casing 1010 has a mixed gas inlet 1010 a for introducing amixed gas into the casing 1010 in the upstream side (left side in thefigure), a non-permeate gas outlet 1010 b in the downstream side (rightside in the figure) and a permeate gas outlet 1010 c in its side wall.The number of the permeate gas outlet 1010 c can be one or two or more.The permeate gas outlets 1010 c can be disposed at regular intervalsalong the side wall of the casing 1010.

The mixed gas introduced from the mixed gas inlet 1010 a enters intoeach hollow fiber membrane 1014 from the end face of the tube sheet 1021and flows downstream in the inside. A part of the mixed gas permeatesthe hollow fiber membrane 1014, and the permeate gas is fed to theinside of the closed space 1018 and then discharged from the casingthrough the permeate gas outlet 1010 c. On the other hand, anon-permeate gas not permeating the hollow fiber membrane as it is flowsdownstream in the hollow fiber membrane 1014 and flows outward from theend face, and then is discharged out of the casing through thenon-permeate gas outlet 1010 b.

The mixed gas inlet 1010 a and/or the non-permeate gas outlet 1010 b canbe disposed in such a way that their central axes are aligned with thecentral axis of the casing 1010 (that is, the central axis of the hollowfiber bundle 1015). The casing 1010 can have a cylindrical member 1011and cap members 1012 at its ends as in the example in FIG. 26 (the otheris not shown). The cylindrical member 1011 and the capping member 1012can be, for example, made of a metal.

Specifically, the cylindrical member 1011 is a hollow member with aninner diameter of do, and has thick wall portions 101 a, 1011 b near itsend. The first thick wall portion 1011 a is formed near the end face ofthe cylindrical member 1011, and has an inner diameter shorter than theinner diameter d₀. The second thick wall portion 1011 b is formed in aninner area in an axial direction than the first thick wall portion 1011a, and has an inner diameter shorter than the inner diameter do. Aninner diameter of a portion between the thick wall portion 1011 a and1011 b is longer than inner diameter of both thick wall portions 1011 a,1011 b; for example, it can be d₀.

Corresponding to the structure of the cylindrical member 1011, the tubesheet 1021 is formed in the following shape. The tube sheet 1021includes generally three parts with different diameters (starting fromthe outer side, the first part 1021 a, the second part 1021 b and thethird part 1021 c) as shown in FIG. 26. Among these parts, the middlepart 1021 b has the largest diameter. In this example, the boundarybetween the first part 1021 a and the second part 1021 b is a taperedface. The boundary between the second part 1021 b and the third part1021 c is a straight face (the face extending in a direction orthogonalto the central axis of the cylindrical member).

When the separation membrane module 1001 is used, a pressure of a mixedgas applies a force to the tube sheet 1021 in a direction that the thetube sheet is pushed into the cylindrical member 1011. However,according to the configuration as shown in FIG. 26, a part of the tubesheet 1021 can abut on the thick wall portion 1011 b to restrictmovement of the tube sheet 1021, so that the tube sheet 1021 is notmoved into the inside.

There can be, but not limited to, an R-shape on the corner 1021 fbetween the second part 1021 b and the third part 1021 c in the tubesheet. Thus, stress concentration can be relaxed in this part, so thatbreakage of the tube sheet and so on can be prevented.

The example in FIG. 26 shows the state where the tube sheet 1021 is athermosetting resin and the tube sheet 1021 has a slightly reduceddiameter due to cure shrinkage. In this configuration, sealing betweenthe tube sheet 1021 and the cylindrical member 1011 may not be ensured.Therefore, an annular sealing member 1060 for sealing between thesemembers is provided with the module in this embodiment.

An annular step 1021 s is formed in the outer circumference of the firstpart 1021 a of the tube sheet as shown in FIG. 26. An annular concavegroove C1 as a whole is formed by the cooperation of the step 1021 s andthe inner surface of the cylindrical member 1011. An annular sealingmember 1060 is disposed in the concave groove C1.

The sealing member 1060 is an annular component made of elasticsmembers, which can be fitted into the concave groove C1 (for example, anO-ring). Alternatively, a resin material for sealing can be injectedinto the concave groove C1 and cured therein, to form the sealingmember. The O-ring can have a circular or elliptic cross-sectionalshape. Examples of an “annular part consisting of elastic members” can,in addition to an O-ring, include a V- or U-packing having asubstantially V- or U-shaped cross section, respectively. Furthermore,its cross section can be rectangular, polygonal or X-shaped. The sealingmember 1060 seals between the tube sheet 1021 and the casing 1010 aswell as between the tube sheet 1021 and the capping member 1012 in theexample shown in FIG. 26.

The structure shown in FIG. 26 is merely an example, which does notlimit this invention in any manner. For example, the first part 1021 aand the third part 1021 c in the tube sheet can have the same diameter.Alternatively, a tube sheet having the first part 1021 a and the thirdpart 1021 c can be used. Furthermore, the surface between the first part1021 a and the second part 1021 b can be, not tapered face as shown inFIG. 26, but a straight face. Likewise, the surface between the firstpart 1021 b and the third part 1021 c can be, not a straight face asshown in FIG. 26, but a tapered face. Furthermore, the sealing member1060 seals between the tube sheet 1021 and the casing 1010 and thecapping member 1012 in the above embodiment, however, there can beadditional sealing member between the casing 1010 and the capping member1012 in addition to the sealing member between the tube sheet 1021 andthe casing 1010

FIG. 27 is a cross-sectional view taken on A-A line of FIG. 26. Concaveportions 1011 d, 1011 d can be formed at two positions on the innersurface of the cylindrical member 1011 as shown in the figure. In thisconfiguration, the material for tube sheet enters the concave parts 1011d, 1011 d and then is cured (detailed below). Consequently, rotation ofthe tube sheet 1021 can be prevented. There are no particularrestrictions to the number of the concave parts 1011 d, for example,one, or three or more.

As an example, the following process can be used for producing the gasseparation membrane module 1001 having the configuration as describedabove. Specifically, a production process according to this embodimentincluding;

(a) applying material for releasing mold to at least a part which is tobe in contact with a tube sheet in the inner surface of a casing,

(b) injecting thermosetting resin before curing into a part of thecasing,

(c) curing the injected thermosetting resin to form the tube sheet, and

(d) providing an annular sealing member between the outer circumferencesurface of the tube sheet and the inner surface of the casing after thecuring of the thermosetting resin.

By applying the material for releasing mold in step (a), the tube sheetmade of for example epoxy resin can be smoothly released from the casing(for example, made of a metal) in the curing of step (c). If it is notused, the tube sheet may not be released in the resin curing step,cracks may be formed in the tube sheet.

In step (b), a not-shown mold can be attached to the end of thecylindrical member 1011 during tube sheet resin is injected. In thisprocess, the mold can has an annular convex part corresponding to thestep 1021 s in the tube sheet (see FIG. 26) to for the step 1021 s inthe tube sheet.

In step (d), an annular elastic member such as an O-ring can be fittedinto the concave groove C1 as described above, or alternatively someresin can be injected into the concave groove C1 and cured to form thesealing member 1060.

According to the gas separation membrane module 1001 as described asdescribed above in this embodiment, the separate sealing member 1060 canensure sufficient sealing between these members, even if cure shrinkageof the tube sheet 1021 may cause insufficient sealing between the outersurface of the tube sheet and the inner surface of the casing,

This is particularly advantageous in a gas separation membrane moduleused at high temperature. That is, generally, material resistant to cureshrinkage tends to be elastic, have a lower glass-transition temperatureand be less heat-resistant. On the other hand, tube sheet material withexcellent heat resistance tends to be susceptible to cure shrinkage. Ifsuch heat-resistant material is used in some structures such as the tubesheet is configured to adhere to the casing, cracks might be formed inthe tube sheet due to drawing stress generated by the shrinkage of thetube sheet material. In contrast, according to this embodiment, thematerial for mold release is applied to the inside of the casing toprevent adhesion of tube sheet material, whereas the sealing between thetube sheet and the casing is ensured by the annular sealing member.Therefore, there can be provided a gas separation membrane module inwhich crack formation is prevented in a tube sheet and sealing isadequately ensured.

Although of the tube sheets 1021, 1022, mainly the tube sheet 1021 (FIG.26) has been described, both tube sheets 1021, 1022 can have the samesimilar configuration. Alternatively, only one tub sheet can has thesheet can has the structure as shown in FIG. 26. Furthermore, thestructures of a tube sheet, an annular sealing member and a casing a sin this embodiment can be applied, besides a bore feed type module, ashell feed type module and other types of modules.

The summary of the main invention disclosed in section G is as follows.

[1] A gas separation membrane module according to one embodiment of theinvention in this section comprises;

a hollow fiber bundle as a collection of a collection of a number ofhollow fiber membranes with gas separation ability,

a casing housing said hollow fiber bundle, and

a tube sheet for fixing at least one end of said hollow fiber bundle,

wherein the outer surface of said tube sheet does not contact to theinner circumference surface of said casing,

further comprising a sealing member for sealing between the outersurface of said tube sheet and the inner surface of said casing.

[2] The gas separation membrane module as described in [1], wherein saidtube sheet has a step for forming an annular concave groove bycooperating with the inner surface of said casing.

[3] The gas separation membrane module as described in [1] or [2],

wherein said casing comprises; a tubular member surrounding said hollowfiber bundle and a capping member at the end of the tubular member,

said tubular member comprises a thick wall portion partially havingshorter inner diameter, the thick wall portion abuts on said tube sheetto prevent movement of said tube sheet in said tubular member toward theinside from an axial direction.

[4] The gas separation membrane module as described in any of [1] to[3], wherein said sealing member is an annular elastic member which isfitted into said annular concave groove.

[5] A process for manufacturing a gas separation membrane moduleaccording to one embodiment of the invention in this section is aprocess for manufacturing a gas separation membrane module, comprising ahollow fiber bundle as a collection of a number of hollow fibermembranes with gas separation ability, a casing housing said hollowfiber bundle, and a tube sheet for fixing at least one end of saidhollow fiber bundle, including;

applying material for releasing mold to at least a part which is to bein contact with said tube sheet in the inner surface of said casing,

filling thermosetting resin in a part of said casing,

curing said thermosetting resin to form said tube sheet, and

forming, after said curing of said thermosetting resin, a sealing memberbetween the outer surface of said tube sheet and the inner surface ofsaid casing.

EXAMPLES Examples Related to Section A

The invention in section A will be further described with reference toexamples. The invention in section A is, however, not be limited to thefollowing examples.

Method for Measuring a Glass-Transition Temperature (Tg) of a HollowFiber Membrane

A glass-transition temperature (Tg) was measured for a sample of 2 mgover a temperature range of room temperature to 400° C. at a rate of 10°C./min under a nitrogen atmosphere using DSC50 device from ShimadzuCorporation in accordance with JIS K7121 “Method for measuring anextrapolated glass transition onset temperature”.

Method for Measuring a Shape-Retention Ratio of a Hollow Fiber Membrane

In measurement of a shape-retention ratio, a hollow fiber having alength of 200 mm was placed in a hot air oven at 175° C. for 2 hours,and a length before and after heating were measured. A shape-retentionratio was determined as a proportion of a length after heating to anoriginal length before heating.

Method for Measuring a Solution Viscosity

A solution viscosity of a polyimide solution was measured at atemperature of 100° C. using a rotating viscometer (rotor shear rate:1.75 sec⁻¹).

Production Example 1

In a separable flask equipped with a stirrer and a nitrogen-gas inlettube, 200 mmol of 4,4′-(hexafluoroisopropylidene)-bis(phthalicanhydride), 225 mmol of 3,3′,4,4′-biphenyl tetracarboxylic dianhydride,75 mmol of pyromellitic dianhydride, 250 mmol of2,2′,5,5′-tetrachlorobenzidine and 250 mmol of3,7-diamino-dimethyldibenzothiophene=5,5-dioxide were placed in 1882 gof 4-chlorophenol as a solvent, and the mixture was subjected topolymerization and imidization at a reaction temperature of 190° C. for20 hours under stirring while nitrogen gas was flowing in the flask, toprepare an aromatic polyimide solution with a polyimide concentration of17% by weight. This aromatic polyimide solution has a solution viscosityof 1940 poise at 100° C.

The aromatic polyimide solution thus prepared was filtered through a 400mesh woven wire. Using the solution as a dope solution and a spinningapparatus equipped with a nozzle for hollow-fiber spinning, the dopesolution was discharged from a circular opening of the nozzle forhollow-fiber spinning (an outer diameter of the circular opening: 1000μm, a slit width of the circular opening: 200 μm, an outer diameter ofthe core opening: 400 μm) while nitrogen gas was fed from the coreopening, to form a hollow fiber form, which was then carried under anitrogen atmosphere, immersed in a coagulation liquid to be solidified,and taken by a take-up roll to provide a wet hollow fiber membrane.Then, this hollow fiber membrane was dried and further heated at 250° C.for 30 min to give a hollow fiber membrane 1.

The hollow fiber membrane 1 thus prepared generally had an outerdiameter of 410 μm and an inner diameter of 280 μm. A fiber bundleelement was formed from the hollow fiber membranes and further a gasseparation membrane module was formed from each fiber bundle elementcomprising the hollow fiber membranes.

Examples 1, 2 used an air separation membrane module 1 which is producedusing the hollow fiber membranes 1 prepared as described above, andComparative Examples 1, 2 used an air separation membrane module 2 whichis produced using a hollow fiber membrane 2 described below or an airseparation membrane module 3 which is produced using a hollow fibermembrane 3.

Table 1 shows data such as properties of each hollow fiber membrane. Aglass-transition temperature and a shape-retention ratio were determinedas described above.

TABLE 1 Inner Outer diameter diameter of a Glass Shape Hollow Materialof of a hollow hollow fiber transition retention P′_(O2)*² fiber ahollow fiber fiber membrane membrane temperature ratio (×10⁻⁵ cm³ (STP)/membrane membrane (μm) (μm) (° C.) (%) cm² · sec · cmHg) 1 Polyimide 410280   300>^(*1)  99.5 9 2 Polysulfone 386 200 190 93 4.9 3Polyetherimide 160 95 223 99 4.5 ^(*1)The hollow fiber membrane 1 doesnot have a glass transition temperature at 300° C. or lower and cannotbe determined by the method described above. ^(*2)P′_(O2) is an oxygenpermeation rate at 40° C.

Table 2 shows the specification of each air separation membrane module.

TABLE 2 Air separation Inner diameter Effective Number Membrane membraneof a vessel length of fibers area module (mm) (mm) in a module (m²) 1 40249 3500 1.12 2 40 496 3800 2.28 3 40 223 18000 2.02

Example 1 of Section A

An air at 175° C. and a pressure of 0.2 MPaG was fed to the airseparation membrane module 1, regulating the air-feed rate such that anoxygen gas concentration in a non-permeate gas, that is, a nitrogen-richair, was 12%, and the process continuously proceeded under theseconditions. At predetermined elapsed times from the beginning of theoperation, a flow rate of the nitrogen-rich air produced was measured.The measurement results are shown in FIG. 1. From the measurementresults, an oxygen permeation rate (P′_(O2)) of the air separationmembrane and a ratio of an oxygen-gas permeation rate to a nitrogen-gaspermeation rate (P′_(O2)/P′_(N2)) as an index of separation performancewere calculated at 0, 140 and 2069 hours after the beginning of theoperation. The results are shown in Table 3.

At the beginning of the operation (0 hr), P′_(O2) was 35.4×10⁻⁵ cm³(STP)/crm-sec cmHg and a flow rate of the nitrogen-rich air producedfrom the air separation membrane module 1 was 0.748 Nm³/h. At 140 hrsafter the beginning of the operation, P′_(O2) was 33.4×10⁻⁵ cm³(STP)/cm²·sec·cmHg which was lower only by 5.6% from the beginning ofthe operation. At 2069 hrs after the beginning of the operation, P′_(O2)was 31.4×10⁻⁵ cm³(STP)/cm²·sec·cmHg which was lower by 11% from thebeginning of the operation. A flow rate of the nitrogen-rich airproduced from the air separation membrane module 1 after 2069 brs fromthe beginning of the operation was 0.65 Nm³/h, which was lower only by13% compared with the beginning of the operation. The results indicatethat even after operation at 175° C. for 2000 hrs, the air separationmembrane module 1 maintained its ability as a gas separation membrane.

Comparative Example 1 of Section A

Although measurement as described in Example 1 was attempted using theair separation membrane module 2, a hollow fiber membrane was soshrinked at 175° C. that a nitrogen-rich air could not be obtained. Inthe air separation membrane module 2 maintained at 175° C., hollowcollapse, fiber breakage and distortion of a tube sheet were observed.

Comparative Example 2 of Section A

Operation was conducted and a flow rate of a nitrogen-rich air at eachpredetermined time was measured as described in Example 1, except thatthe air separation membrane module 3 was used. The measurement resultsare shown in FIG. 1. P′_(O2) at the beginning of the operation was19.3×10 cm³(STP)/cm²·sec·cmHg and a flow rate of a nitrogen-rich airproduced from the air separation membrane module was 0.625 Nm³/h. At 140hrs after the beginning of the operation, P′_(O2) of the separationmembrane was 11.3×10⁻⁵ cm³(STP)/cm²·sec·cmHg, which was lower by 41%from the beginning of the use, and a flow rate of a nitrogen-rich airproduced from the air separation membrane module was 0.419 Nm³/h, whichwas lower by 35% from the beginning of the use.

Example 2 of Section A

Measurement was conducted as described in Example 1, except that theair-feed rate was regulated such that an oxygen gas concentration in anitrogen-rich air produced was 5%. The measurement results are shown inFIG. 2. A flow rate of a nitrogen-rich air at the beginning of theoperation was 0.18 Nm³/h. At 2069 hr after the beginning of theoperation, a flow rate of a nitrogen-rich air was 0.15 Nm³/h, which waslower only by 16%. The results indicate that, as in Example 1, the airseparation membrane module 1 maintained its performance as a gasseparation membrane even after 2000 hr at 175° C.

TABLE 3 <Flow rate of a nitrogen-rich air and properties of an airseparation membrane after predetermined times at 175° C.> Hollow 0 hr140 hr 2069 hr fiber Product P′_(O2)/ Product P′_(O2)/ Product P′_(O2)/membrane amount P′_(O2) P′_(N2) amount P′_(O2) P′_(N2) amount P′_(O2)P′_(N2) 1 0.748 35.4 2.6 0.717 33.4 2.6 0.650 31.4 2.5 2 Not measureableNot measureable Not measureable 3 0.625 19.3 2.7 0.419 11.3 3.0 — — —

In this table, the product amount is a flow rate of a nitrogen-rich airproduced (the unit is Nm³/h).

P′_(O2) is an oxygen-gas permeation rate (the unit thereof is ×10⁻⁵cm³(STP)/cm²·sec·cmHg).

P′_(O2)/P′_(N2) is a ratio of an oxygen-gas permeation rate to annitrogen-gas permeation rate.

Example Related to Section B

The invention in section B will be described with reference to examples,but the present invention is, however, not be limited to the examples.

Example 1 Preparation of a Casting Resin Composition

A mixture of 100 parts by weight of phenol novolac polyglycidyl etherand 10 parts by weight of a carboxyl-terminated butadiene⋅acylonitrilecopolymer (molecular weight: 3100) was heated at 150° C. for 3 to 4hours to prepare a denatured epoxy resin. Then, 100 parts by weight ofthe denatured epoxy resin thus prepared, 80 parts by weight ofmethyl-5-norbornene-2,3-dicarboxylic anhydride and 0.3 parts by weightof 2-ethyl-4-methylimidazole were mixed and stirred to prepare a castingresin composition.

Evaluation of Moldability of a Tube Sheet

A fiber bundle as a collection of 12,000 polyimide hollow fibermembranes (length: 100 cm, outer diameter: 500 μm) was placed in a moldwith Φ100 mm as shown in FIG. 4b . The fiber bundle was substantiallyerected in such a way that the tip was down, and the casting resincomposition prepared by the above procedure was slowly injected into amold kept at 70° C. The amount of the casting resin composition wasregulated such that a thickness became about 90 mm. After the injection,the composition was first-cured at 70° C. for 12 hours, then heated to142° C. and then post-cured for 4 hours, to mold the tube sheet. Afterthe curing, the hollow fiber element was removed from the casing andvisually observed, and the tube sheet was cut substantially into halvesand the state of the center was visually observed.

As a result, no cracks were observed in the molded tube sheet.

Example Related to Section E

There will be described the results of simulation with respect to aresponse of a gas separation membrane module with or without film memberwrapping. Table 4 shows module response, in which “type A (crossflow)”indicates a module without film member wrapping, “type B (counterflow)”indicates a module with film member wrapping. Calculation was conductedwith the temperature of t=25° C. and the mixed-gas feed pressure PF=0.7MPaG. It is noted that the simulation was conducted for a separationmembrane module for producing a nitrogen-rich air as a product from airfed as the mixed gas. This nitrogen-rich air passes through the hollowfiber membrane and recovered as a non-permeate gas discharged from thedownstream end. In the table, a feed pressure and a feed flow rateindicate a feed pressure and a feed flow rate of the air as a mixed gas,respectively; a product concentration and a product flow rate indicate anitrogen concentration and a flow rate of a nitrogen-rich air as aproduct as a non-permeate gas, respectively; and a recovery rateindicates a proportion of a non-permeate gas as a product in the mixedgas fed (product rate/feed flow rate)×100.

TABLE 4 Product Temp. Feed Feed flow concentration Product flow tpressure rate FF XR rate FR Recovery Type Flow Case ° C. PF MPaGNmm^(3/)h % N₂ Nm³/h rate Remarks A Crossflow 1 25 0.7 131.9 95 62.047.0 B Counterflow 2 25 0.7 131.9 96.05 61.5 46.6 FF equal to that in 13 25 0.7 144.8 95 73.2 50.6 XR equal to that in 1

As shown in Table 4, at the same feed flow rate FF (see cases 1 and 2),the case 2 with film member wrapping can provide higher productconcentration XR. At the same product concentration XR (see cases 1 and3), the case 3 with film member wrapping can provide higher product flowrate and a higher recovery rate. In other words, these results indicatethat wrapping with a film member is effective in efficient gasseparation.

EXPLANATION OF REFERENCES

-   -   1, 1′, 101: separation membrane module    -   10, 110, 110′: cylindrical vessel    -   10 a: inner surface of vessel    -   10 f: flange    -   10 h: opening    -   10 s: step    -   10 t: step    -   110 g: groove    -   111: tubular member    -   112: end member    -   12, 112 h: permeate gas outlet    -   112 f: flange    -   14: hollow fiber membrane    -   15, 115: hollow fiber bundle    -   17: annular sealing member    -   18, 118, 119: O-ring    -   20, 21, 26, 27, 120, 121, 127: cap    -   20 h: opening    -   120 f flange    -   120 s: step    -   22A: mixed gas inlet    -   22B: non-permeate gas outlet    -   27 f: flange    -   127 f: flange    -   127 g: groove    -   30, 30′, 38, 130A, 130B, 530: tube sheet    -   30 s, 530 s: step    -   30′t: step    -   41: discharge pipe    -   42: fixing screw    -   43: fixture    -   201: gas separation membrane module    -   210: cartridge    -   211: cylindrical vessel    -   212: opening    -   214: hollow fiber membrane    -   215: hollow fiber bundle    -   217, 218: inner groove    -   219: periphery groove    -   220, 221: capping member    -   220A: end face    -   220B: cylindrical part    -   220 f: flat part    -   220 g: flat part    -   220 h: through-hole    -   223: outlet    -   227 a, 227 b: inner groove    -   230, 231: tube sheet    -   R1, R2: elastic ring member    -   245: fixing rod    -   246: nut    -   P1: gas inlet    -   P2: non-permeate gas outlet    -   P3: gas channel    -   601: gas separation membrane module    -   610: casing    -   610 a: mixed gas inlet    -   610 b: non-permeate gas outlet    -   610 c: permeate gas outlet    -   611: tubular member    -   612, 613: cap    -   614: hollow fiber membrane    -   615: hollow fiber bundle    -   618: closed space    -   619 a: mixed gas space    -   619 b: non-permeate gas space    -   621, 622: tube sheet    -   631: film member    -   631 a, 631 b: end    -   801: gas separation membrane module    -   810, 910: casing    -   810 a, 910 a: mixed gas inlet    -   810 b, 910 b: non-permeate gas outlet    -   810 c, 910 c: permeate gas outlet    -   910 d: purge gas inlet    -   811: tubular member    -   813: tube sheet retaining member    -   813 a: straight part    -   813 b: longer diameter part    -   813 c: tapered part    -   814, 914: hollow fiber membrane    -   815, 915: hollow fiber bundle    -   818, 918: closed space    -   819 a: mixed gas space    -   819 b: non-permeate gas space    -   821, 822, 921, 922: tube sheet    -   822 a: hollow-fiber-membrane burying part    -   822 b: tube sheet intact part    -   831: film member    -   831 a, 831 b: end    -   850, 950: sealing structure    -   851, 853: sealing part    -   855: fixing tape    -   857: fixture    -   891, 893: filler    -   971: core tube    -   971 a: hole    -   A1: exposed part    -   A31: gap    -   1001: gas separation membrane module    -   1010: casing    -   1010 a: mixed gas inlet    -   1010 b: non-permeate gas outlet    -   110 c: permeate gas outlet    -   1011: cylindrical member    -   1011 a, 1011 b: thick wall portions    -   1011 d: concave part    -   1012: capping member    -   1014: hollow fiber membrane    -   1015: hollow fiber bundle    -   1018: closed space    -   1019 a: mixed gas space    -   1019 b: non-permeate gas space    -   1021, 1022: tube sheet    -   1021 s: step    -   1060: sealing member    -   C1: annular concave groove    -   B11: mixed gas inlet    -   B12: permeate gas outlet    -   B13: non-permeate gas outlet    -   B14: hollow fiber membrane    -   B15: casing    -   B16 a, 16 b: tube sheet    -   B21: mold    -   B22: casing    -   B23: tube sheet    -   B24: hollow fiber membrane

1. A gas separation membrane module, comprising: a hollow fiber bundleincluding a number of hollow fiber membranes with selectivepermeability; a cylindrical vessel housing the hollow fiber bundle; atube sheet placed at the end of the hollow fiber bundle, bonding thehollow fiber membranes together; a cap member attached to an end of thecylindrical vessel, and a first annular sealing member for sealing a gapbetween the outer surface of the tube sheet and the inner surface of thecap member; wherein the tube sheet does not comprise a stepped portionat its periphery on which the first annular sealing member is to bemounted.
 2. The gas separation membrane module according to claim 1,further comprising: a second annular sealing member for sealing a gapbetween a flange portion of the cap member and a flange portion of thecylindrical vessel.
 3. The gas separation membrane module according toclaim 2, wherein the flange portion of the cap member and the flangeportion of the cylindrical vessel are connected by using a bolt-nutsystem.
 4. The gas separation membrane module according to claim 2,wherein the flange portion of the cap member and the flange portion ofthe cylindrical vessel are connected by using a bolt which is screwedinto a threaded hole formed at the flange portion of the cylindricalvessel.